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LABORATORY MANUAL 



Inorganic Preparations 






H. T. VULTE, Ph. D , F. C. S. 

'ROFESSOR OF CHEMISTRY IN BARNARD COLLEGE, AND ASSISTANT IN CHEMISTRY AT TH1 
SCHOOL OF MINES, COLUMBIA COLLEGE, N. Y. 



GEORGE M. S. NEUSTADT 




£DHH0 







NEW YORK 
GEO. GOTTSBERGER PECK, Publisher 



II MURRAY STREET 



1895 



& 



^ 



Entered, according to Act of Congress, in the year 1895, 

By GEO. GOTTSBERGER PECK, 

In the Office of the Librarian of Congress, at Washington. D. C. 



?f.f 



PRE FACE 



The study of inorganic chemistry naturally precedes that of 
organic, and in a certain way this plan is carried out in a com- 
plete chemical course. The study of the organic branch, how- 
ever, proceeds on a much more logical plan than that usually 
adopted in inorganic work; one of the chief advantages being 
the practical work, to which the student is introduced very 
early in his course. The following work is synthetic, and shows 
how compounds, often very complex in character, rare in occur- 
rence or expensive in preparation, may be produced from simple 
substances, or from those which are comparatively plenty and 
cheap, and at the same time the bye products may be saved. 
Such a course of study is also of great value in inorganic work, 
but should precede and lead up to, and not follow organic chem- 
istry. However, a contrary plan seems to have been followed, 
for while we have various works on organic preparations, there 
are none, so far as the authors know, in the inorganic branch 
of the subject (at least not in English), excepting the works on 
Elementary Chemistry; and where these treat of the subject in 
laboratory practice, the methods are those which cannot be 
recommended as the best and most economical. 

In many laboratories the waste of material is greater than the 
use. Students are apt to acquire the idea that after a certain re- 
sult has been produced the rest of the material is worthless, and 
in consequence much loss occurs from throwing away valuable 
substances, which can be recovered or used with little trouble or 
expense. It is not a very difficult operation to purify the various 
commercial salts, converting them into C. P. reagents, and in the 
operation the student cannot help acquiring facts which are 
directly and forcibly brought to his knowledge. Too much reli- 
ance is usually placed on the so-called C. P. chemicals in com- 
mon use. Many are high-priced and apt to deteriorate in the 



11 PREFACE. 

packages. There is no reason why the student should not pre- 
pare many of these, unless it be that he does not always know 
where to look for the necessary information. 

The book is designed to meet a long felt want in the inor- 
ganic laboratory, in training the student to prepare his own 
reagents and to test them for the customary impurities. The 
methods are largely those in commercial use, and should prove 
of value to those studying Applied Chemistry. 

'lhe works of Fresenius, Erdmann and others, as well as the 
various chemical journals for some years past, have been carefully 
searched, and such information as was thought valuable has been 
collected and arranged in order, beginning with the simplest 
operations and gradually increasing in difficulty as the student 
acquires skill in his work. As far as possible, references to the 
original articles have been given. 

October, 1895. 



LABORATORY MANUAL 



OF 



INORGANIC PREPARATIONS, 



WATER. 
H 2 0. 

Pure water is obtained by distilling spring water from 
a copper still with head and condenser made of pure 
tin. The distillation is carried to about three-fourths 
of the quantity operated upon. If it is desired to have the 
distilled water perfectly free Irom carbonic acid and am- 
monium carbonate, the portions passing over first must be 
rejected. In the larger chemical laboratories, distilled 
water is obtained from the steam apparatus which serves 
for drying, etc. Rain water collected in the open air may 
in many cases be substituted for distilled water. 

It must be colorless, odorless, and tasteless, and 
should not leave the smallest residue when evaporated in a 
platinum vessel. It should not be changed by ammonium 
sulphide (copper, lead, iron), nor rendered turbid by baryta 
water (carbonic acid). No cloudiness should be caused 
even after long standing by the addition of ammonium 
oxalate, of barium chloride and hydrochloric acid (sul- 



2 LABORATORY MANUAL OF 

phuric acid), of silver nitrate and nitric acid (chlorides), or 
of mercuric chloride and sodium carbonate (ammonia). 

We use water principally as a simple solvent for a great 
variety of substances. 

AMMONIUM— FREE WATER. 

If the ordinary distilled water gives a reaction for am- 
monia with Nessler's reagent, it should be treated with 
sodium carbonate, about one gram to the litre and boiled 
until one-fourth has been evaporated. 

Ammonium free water may also be prepared by dis- 
tilling water made slightly acid with sulphuric acid. 

WATER FREE FROM ORGANIC MATTER AND AMMONIA.* 

About 15-20 litres of ordinary distilled water, to which 
about 1 gram, of potassium hydrate and 0.2 gram, of 
potassium permanganate have been added are maintained 
at about 100 C. for twenty-four hours under an inverted 
condenser, after which the condenser is reversed and the 
water distilled off. Apply Nessler's test to the distillate 
from time to time, until 100 c.c. show no coloration and 
collect that which comes over subsequently, stopping 
50OCC. short of dryness. 

As an additional precaution the water thus obtained 
may be acidified with sulphuric acid and re-distilled. 

For preparing distilled water, the ordinary tin lined 
copper still and block tin condenser may be used, or a 
more economical way is to make use of the well known 
Domestic Water Still, (Fig. 1). This piece of apparatus 

* Water Analysis, Frankland, p. 113. 



INORGANIC PREPARATIONS. 



yields a good quality of product, with a minimum ex- 
penditure of heat and condenser water, and is moreover 
very compact. 




Fig. l. 

Water free from organic matter and ammonium, which 
is indispensable in water analysis and the preparation of 
many standard solutions such as potassium permanganate, 
argentic nitrate etc., is best prepared in the apparatus 
shown in. Fig 2, which consists of a glass-stoppered flask 
with side-neck tube. The end of the side-neck tube is turned 
vertically downward, being thrust deeply into the tin tube 
of the condenser, and held in place there by a short piece of 
rubber tubing. The three-eighth inch block tin pipe forming 
the condenser-tube is bent zigzag instead of in the conven- 



4 LABORATORY MANUAL OF 

tional helix. This affords a more even flow of the distillate. 
The cylindrical copper jacket containing the water for cool- 
ing is about four inches in diameter, and fifteen inches long. 
The disk closing the lower end is arched upward so that in 




Fig. 2. 



case the condenser " sweats " from the use of very cold 
water, the drip from the outside can not contaminate the 
distillate. The lower end of the tin tube is cut aslant for 
the more certain delivery of the distillate. 



INORGANIC PREPARATIONS. 



ETHYL ALCOHOL. 
C 2 H 5 .OH. 

Two sorts of alcohol are used in chemical analy- 
sis, viz.: ist, Commercial "95 per cent, alcohol," 
which really contains 93 to 94 per cent, of alcohol 
by weight ; and 2d, absolute alcohol. The latter may be 
prepared most conveniently by placing in a flask or tin can 
800 grams of good quick-lime in coarse powder or small 
lumps, adding 1 litre of " 95 per cent, alcohol," connecting 
the vessel with the lower end of a Liebig condenser, and 
keeping its contents boiling on a water bath for an hour. 
The can is then connected to the upper end of the conden- 
ser, and the dehydrated alcohol distilled off into a bottle 
for use.* 

Pure alcohol must completely volatilize, and ought 
not to leave a smell of fusel-oil when rubbed between 
the hands ; nor should it alter the color of moist blue or 
red litmus paper. When kindled, it must burn with a faint 
bluish, barely preceptible flame. 

Commercial Alcohol invariably contains aldehyde and 
if kept in tin cans stannic oxide as well; such alcohol can- 
not be used for the preparation of alcoholic potash solutions, 
argentic nitrate or for Hiibl's iodo-mercuric chloride 
solution. For such purposes either of the two following 
methods may be used. 

A convenient amount of the alcohol to be purified is 
shaken with pulverized potassium permanganate until it 
assumes a decided color. It is then allowed to stand for 



Erlenmeyer ; J. Lawrence Smith. 



6 LABORATORY MANUAL OF 

some hours, until the permanganate has been decomposed 
and brown manganese oxide is deposited. A pinch of 
pulverized calcium carbonate is then added, and the alcohol 
distilled at the rate of about 50 c. c. in 20 minutes from 
a flask provided with a Wurtz tube or one of the Lebel- 
Heninger pattern. The distillate is tested frequently until 
about 10 c. c. thereof, when boiled with 1 c. c. of strong 
(syrup) solution of caustic soda or potash, gives no percept- 
ible yellow coloration on standing for 20 minutes or half 
an hour. What distills over after that time is preserved for 
use. 

The first distillates may be added to the small amount 
remaining in the distilling flask (which should not be driven 
down to the complete dryness), and a fresh portion of puri- 
fied alcohol recovered. 

The rationale of the proceeding appears to be that the 
permanganate oxidizes and destroys chiefly the fusel-oil, 
furfurol and other compounds of that nature, the acids 
resulting from the reaction are neutralized by the calcium 
carbonate added before distillation, and by distilling 
slowly the aldehyde at least is concentrated in the first 
portions of the distillate. Distillation of alcohol contain- 
ing caustic potash or soda seemed to cause a constant 
formation of aldehyde. The alcohol thus purified is per- 
fectly neutral, and gives most satisfactory results when 
used as a solvent for caustic alkalies or silver nitrate, the 
solutions remaining as colorless as distilled water, even 
after boiling and standing indefinitely, if properly pro- 
tected from dust and other external influences.* 



Jour. Am. Chem. Soc. — E. Waller. 



INORGANIC PREPARATIONS. 



The second method consists in distilling the alcohol 
with some caustic potash in the presence of a large quantity 
of non-volatile fatty acid ; either oleic or stearic is gener- 
ally used, the process is simple and the result good. 



OXYGEN. 
O. 

The compressed gas put up in steel cylinders is 
sufficiently pure for most purposes, but when not avail- 
able the gas may be readily prepared by heating a mixture 
of equal parts of potassium chlorate and manganese di- 
oxide, in a copper retort, or better, in an apparatus similar 
to fig. 3. 




Fig. 3. 

Oxygen gas made in this way is liable to contain 
chlorine or oxides of chlorine and carbon dioxide, it is 
purified by washing with potassium hydrate and dried by 
passing through concentrated sulphuric acid. 

Oxygen may also be prepared by treating sodium 
dioxide Na 2 2 with dilute acid, either hydrochloric or 
sulphuric. 



8 LABORATORY MANUAL OF 

Na 3 2 + 2H.C1 = O + 2NaCl + H s O, 

great heat is evolved in this reaction and the operation 
must be conducted with care; it is however an excellent way 
to oxidize solutions, in which case the solution is made acid 
and the sodium dioxide dropped in and well stirred until 
the desired effect has been produced. 

In the wet way oxygen is produced by treating 
"Chloride of Lime " Ca(C10) 2 ,CaCl 3 in disc form, in a Kipp's 
Apparatus with a mixture of I litre of hydrogen dioxide and 
53 c. c. nitric acid com. Sp. Gr. 1.265. The same pre- 
cautions for purification are necessary as in the case of 
manganese dioxide and potassium chlorate. 

To prepare oxygen, cubes consisting of a mixture of 
2 parts of barium dioxide, 1 part of manganese dioxide 
and 1 part of plaster are used with hydrochloric acid (sp. 
gr. 1. 12) diluted with an equal volume of water. The oxy- 
gen evolved contains traces of chlorine and must there- 
fore be washed with an alkali.* 

It can also be prepared by adding potassium perman- 
ganate to hydrogen peroxide made alkaline with ammonia.f 

Oxygen is a colorless gas, and without odor. It is 
liquified with difficulty, requiring a pressure of 320 atmos- 
pheres at 212° F. Oxygen is remarkable for the wide 
range of its chemical attraction for other elementary bodies 
with all of which it is capable of entering into combi- 
nation except one, namely fluorine. 



* G. Neumann, Bcr. 20, 1584. 

f C. F. Gohring, Chem. Zeit. 12, 1659. 



INORGANIC PREPARATIONS. 



HYDROGEN. 
H. 

Hydrogen is best prepared from granulated zinc 
and dilute sulphuric acid (i litre acid, 5 litres water) in 
Kipp's Apparatus ; the zinc should not be too pure or the 
supply of gas will be slow and feeble. In any case it is well 
to add a small amount of copper sulphate solution, just 
sufficient to produce a thin coat of copper on the zinc, 01 
a piece of platinum foil may be used in place of the copper 
sulphate ; in this latter case it is better to amalgamate the 
zinc, by first treating with dilute sulphuric acid and then 
adding mercury and shaking, or by simply treating the 
zinc with a strong solution of mercuric nitrate containing 
free nitric acid. 

A granulated alloy of tin and zinc, containing about 83 
per cent, of the latter, prepared by adding zinc to molten 
tin as long as it dissolves, is recommended for use in 
Kipp's apparatus. The pieces retain their shape and size 
after all the zinc is dissolved out, and therefore have no 
tendency to fall through into the lower bulb.* 

Hydrogen may also be prepared by sodium amalgam 
with dilute acids. 

Hydrogen gas prepared by the action of zinc and acid 
is never pure, but may contain hydrocarbons, hydrogen 
sulphide, sulphur dioxide, etc. 

The very small amount of arsenic generally present, 
as AsH 3 , may be neglected. The other impurities are re- 
moved by first passing the gas through a solution of 



J. Habermann, Zeit. Anal. Chem. i\ 



IO LABORATORY MANUAL OF 

potassium permanganate in order to oxidize hydrocarbons, 
hydrogen sulphide, etc., then through the potassium 
hydrate to absorb carbon dioxide, sulphur dioxide, etc., 
and finally through concentrated sulphuric acid and calcium 
chloride to remove water. 

Hydrogen is a colorless, odorless and tasteless gas, is 
highly combustible, burning with a very hot but slightly 
luminous flame, and when mixed with air or free oxygen, 
explodes with violence. 



NITROGEN. 

N. 

This gas is seldom used, but when required may be 
readily prepared by heating equal parts of concentrated 
aqueous solutions of ammonium chloride and potassium or 
sodium nitrite. 

NH 4 CI + KN0 3 = N 3 + KC1 4- 2H 3 0. 

The operation is conducted in a roomy flask, the out- 
going gas mixed with steam, ammonium chloride, and pos- 
sibly some oxides of nitrogen, is cooled washed with water 
and dried over sulphuric acid. Nitrogen prepared in this 
way contains no argon. 

Nitrogen is a colorless, odorless and tasteless gas, and 
is a non-supporter of combustion. 



CHLORINE AND CHLORINE WATER. 

CI. 
Chlorine is prepared by mixing 18 parts of common 
salt in lumps with 15 parts of finely pulverized good man- 



INORGANIC PREPARATIONS. II 

ganese dioxide, free from calcium carbonate ; put the mix- 
ture in a flask, pour a completely cooled mixture of 45 parts 
of concentrated sulphuric acid and 21 parts of water upon 
it, and shake the flask : a uniform and continuous evolution 
of chlorine gas will soon begin, which, when slackening 
may be easily increased again by the application of a gentle 
heat. This method of WlGGERS is excellent, and can be 
highly recommended. Conduct the chlorine gas evolved 
first through a flask containing a little water, then into a 
bottle filled with cold water, and continue the process until 
the fluid is saturated. Where it is desired to obtain 
chlorine water quite free from bromine, the washing flask 
is changed after about one-half of the chlorine has been 
expelled, and the gas which now passes over is conducted 
into a fresh bottle filled with water. If the chlorine water 
is to be quite free from hydrochloric acid, the gas must be 
passed through a U tube containing manganese dioxide. 
The chlorine water must be protected from the action of 
light ; since, if this precaution is neglected, it speedily suf- 
fers complete decomposition, being converted into dilute 
hydrochloric acid, with evolution of oxygen (resulting from 
the decomposition of water). Smaller quantities, intended 
for use in the laboratory, are best kept in a stoppered 
bottle protected by a case of pasteboard. Chlorine water 
which has lost its strong peculiar odor is unfit for use. * 

CHLORINE FROM CHLORIDE OF LIME IN KIPP'S APPA- 
RATUS. 

Dry chloride of lime is intimately mixed with plaster 
and moistened to such a degree that it can only with diffi- 
culty be rolled into balls between the fingers. It is made 



12 LABORATORY MANUAL OF 

homogeneous by powdering in an iron mortar and beaten 
into an iron frame 10-12 m.m. high by means of an iron 
mallet. It is then covered with a piece of oilcloth and 
submitted to great pressure. The plate of chloride of lime 
is then cut into cubes while still in the frame and dried as 
quickly as possible at 20 C. The cubes are then preserved 
in well-closed vessels. It is used in a Kipp's apparatus 
with hydrochloric acid (sp. gr. 1.124) diluted with an 
equal volume of water. The acid must be free from sul- 
phuric acid.* 

When chlorine is generated from bleaching powder and 
hydrochloric acid in a Kipp's apparatus, it is advisable, af- 
ter using the apparatus, to blow in a little air, otherwise a 
slow but continuous action takes place, owing to the ab- 
sorption of the chlorine by the acid.f 

APPARATUS FOR A CONSTANT SUPPLY OF CHLORINE. 

I. The manganese dioxide is used in fragments the size of 
peas, and is placed in a two-necked bottle, at the bottom 
of which there is a layer of broken glass or pumice. This 
stands in a water bath. Hydrochloric acid is supplied 
from a reservoir at a higher level by a tube reaching to 
the bottom of the layer of glass, a T-piece and stopcocks 
allowing the same tube to serve for the removal of the 
manganese solution. The corks should be soaked in par- 
affin. Suitable drying apparatus can be attached and will 
not require replenishing for a long time. The chlorine 
begins to come off when the temperature of the bath 
reaches 50° C, and by means of a stopcock on the outlet its 



* C. Winkler, Ber. 20, 184. 
f C. Winkler, Ber. 22, 1076. 



INORGANIC PREPARATIONS. I 3 

rate is completely under control. The evolution can 
speedily be arrested by closing the stopcock at the outlet 
of the drying apparatus and emptying the water bath. 

The apparatus is then left full of chlorine, and is ready 
at any moment to give supply of the gas completely free 
from oxygen.* 

II. From sodium chloride, pyrolusite, and sulphuric 
acid. — It is usually supposed that in this reaction the whole 
of the chlorine is evolved in the free state; detailed experi- 
ments have, however, shown that this is not the case, but 
that the reaction which takes place is as follows : 

4NaCl + Mn0 2 + 3H 3 S0 4 = 2NaHS0 4 f Na 3 S0 4 + MnCl 3 + 
2H 3 + C1 3 . 

The necessary proportions are, therefore, 5 parts of 
pyrolusite, 11 parts salt, and 14 parts of sulphuric acid 
diluted with an equal volume of water. 

III. From pyrolusite, hydrochloric and sulphuric acids. 
— The instructions usually given for the preparation of 
chlorine by this method are to take 1 part of pyrolusite, 2 
of hydrochloric acid of sp. gr. 1.14, and 1 part of sulphuric 
acid mixed with an equal bulk of water, the reaction being 
supposed to take place according to the equation: 

Mn0 3 + 2HC1 + H 3 S0 4 = MnS0 4 + 2H 3 + Cl 2 . 

As in the foregoing case this equation is quite incorrect, 
only 65 per cent, of the chlorine being obtained in the free 
state. 



* A. Vosmaer, Zeit. Anal. Chem., 27, 638. 



14 LABORATORY MANUAL OF 



CHLORINE FOR LABORATORY PURPOSES. 

When hydrochloric acid of sp. gr. 1. 1, heated to about 
8o° C, is allowed to come slowly in contact with pieces of 
potassium chlorate which have been previously fused, a 
steady evolution of gas takes place. Under these condi- 
tions, about 82 to 85 per cent, of the gas is chlorine, the re- 
mainder being chlorine dioxide. . Another 10 per cent, of 
the dioxide may be decomposed by passing the evolved 
gas through a saturated hydrochloric acid solution of man- 
ganous chloride at 90 C. If the gas is wanted absolutely 
pure, the gas, after passing through the manganous chlor- 
ide, may be passed through a combustion tube filled with 
asbestos and heated to redness. Care must be taken to 
have the acid hot, and not to allow the action to become 
rapid, or the proportion of chlorine dioxide may become 
much increased and explosion occur. 1 gram of potas- 
sium chlorate yields about half a litre of chlorine. 

If a Kipp or some similar constant gas-generating ap- 
paratus is employed, and the acid heated by a steam 
jacket or by standing the generator in hot water, this 
method forms a convenient constant chlorine apparatus for 
laboratory use.* 

Chlorine is a heavy greenish, yellowish gas, having a 
strong and suffocating odor, and if inhaled in sufficient 
quantities is capable of producing suffocation. Free 
chlorine gas is readily detected by its color and odor. 



F. A. Gooch and D. A. Kreider, Zeit. Anorg. Chem. , 7, 17. 



INORGANIC PREPARATIONS. 



HYDROCHLORIC ACID, OR 
HYDROGEN CHLORIDE. 
HC1. 
Pour a cooled mixture of seven parts of concen- 
trated sulphuric acid and two parts of water over 
four parts of sodium chloride in a retort ; expose the re- 
tort, with slightly raised neck, to the heat of a sand-bath 
until the evolution of gas ceases ; conduct the evolved 
gas, by means of a bent tube, into a flask containing six 
parts of water, and take care to keep this vessel constantly 
cool. To prevent the gas from receding the tube ought to 
dip but about one line into the water of the flask. When 
the operation is terminated, try the specific gravity of the 
acid produced, and dilute with water until it marks from 
I.I I to 1. 12. If you wish to ensure the absolute purity of 
the acid, and its perfect freedom from every trace of arsenic 
and chlorine, you must take care to free the sulphuric acid 
intended to be used in the process from arsenic and the 
oxygen compounds of nitrogen, according to the directions 
(see sulphuric acid, page 22.) A pure acid may also be 
prepared cheaply from the crude hydrochloric acid of com- 
merce by diluting the latter to a specific gravity of 1.12 and 
distilling the fluid with addition of some chloride of sodium. 
Or you may put the acid into the retort in the concentrated 
form, placing 60 parts of water into the receiver for every 
100 parts of concentrated acid, and not luting the receiver 
to the retort. If the crude acid contains chlorine this 
should be removed first by cautious addition of solution of 
sulphur dioxide, before proceeding to the distillation ; if, 



l6 LABORATORY MANUAL OF 

on the other hand, it contains sulphur dioxide, this is re- 
moved in the same way by cautious addition of some 
chlorine water. Hydrochloric acid not unfrequently con- 
tains arsenious chloride, owing to the presence of arsenic 
in the sulphuric acid employed. To free it from this im- 
purity, the acid is mixed with twice its volume of water, 
hydrogen sulphide is conducted into it, the mixture allowed 
to stand at rest for some time, the clear fluid then decanted 
from the sulphur and arsenious sulphide, and heated, to ex- 
pel the hydrogen sulphide. 

Hydrochloric acid must be perfectly colorless and 
leave no residue upon evaporation. If it turns yellow 
on evaporation, ferric chloride is present. It must not im- 
part a blue tint to a solution of potassium iodide mixed 
with starch paste (chlorine or ferric chloride), nor discolor 
a fluid made faintly blue with iodized starch (sulphur 
dioxide). Barium chloride ought not to produce a pre- 
cipitate in the highly diluted acid (sulphuric acid). Hy- 
drogen sulphide must leave the diluted acid unaltered (ar- 
senic). After neutralization with ammonia, ammonium 
sulphide must produce no change in it (iron, thallium). 

It can also be prepared by distilling a mixture of cone, 
sulphuric and hydrochloric acids; this latter method is bet- 
ter where gaseous hydrochloric acid is needed. 

METHODS FOR OBTAINING CONSTANT STREAMS OF HY- 
DROGEN CHLORIDE AMMONIA AND NITROGEN. 

Hydrogen chloride can be generated in a Kipp's ap- 
paratus by the action of ordinary sulphuric acid on carnal- 
lite and ammonia gas by allowing a solution of ammonia 
to react with solid potassium hydroxide. When the ma- 



INORGANIC PREPARATIONS. 



17 



terials are exhausted, the solution of potash which is 
formed may be used for ordinary laboratory purposes after 
it has been boiled to expel ammonia. 

To prepare nitrogen in Kipp's apparatus, it is best to 
employ cubes containing chloride of lime made according 
to Winkler's method (page 11); these are treated with 
a mixture of equal volumes of ammonia and water. 
The resulting gas contains suspended ammonium chloride 
and other impurities, which ma}' be removed by passing 
it through water, potash and sulphuric acid.* 




Fig. i. 



NITRIC ACID. 
HXO3 or N0 2 OH. 

Prepared by slowly distilling a mixture of 5 parts of 
sodium nitrate and 3 parts of cone, sulphuric acid, in an 
apparatus as shown in Fig. 4 ; the product is usually not 



By G. Neumann, (J. pr. Chem. [2] 37, 342-345). 



I 8 LABORATORY MANUAL OF 

sufficiently concentrated, and must be redistilled with five 
times its volume of cone, sulphuric acid in an apparatus 
similiar to the above. If the product is colored yellow or red 
by dissolved oxides of nitrogen, it may be rendered color- 
less by blowinga current of dry air through the acid for some 
minutes. Concentrated nitric acid 1.53 spcific gravity 
has a strong affinity for water and must be kept closely stop- 
pered. 

The sudden frothing which frequently takes place when 
nitric acid is prepared from sodium nitrate and sulphuric 
acid is explained on the assumption that the first portions 
pass over at 84° C, and that the heating must be commenced 
cautiously, and the temperature only allowed to rise after 
the first reaction abates. After the temperature has risen 
above 109 C, no acid passes over until the temperature 
1 1 7 C. is reached, when the last portions pass over. The 
latter acid has a sp. gr. 1.42, and corresponds with the 
hydrate, 2HN0 3 + H 3 0, which distills at 120 to 12 1 ° C. 
without decomposition.* 

Another method of preparation is to heat crude nitric 
acid of commerce, as free as possible from chlorine, and of 
a specific gravity of at least 1.3 1 in a glass retort to 
boiling, with addition of some potassium nitrate ; let the 
distillate run into a receiver kept cool, and try from time 
to time whether after dilution it still continues to precipi- 
tate or cloud solution of silver nitrate. As soon as this 
ceases to be the case, change the receiver, and distill until 
a trifling quantity only remains in the retort. Dilute the 
distillate with water until the specific gravity is 1.2. 



By C. W. Volney, J. Amer. Chem. Soc. 13, 246-251. 



INORGANIC PREPARATIONS. 19 

Another method is to dilute crude nitric acid of com- 
merce of about 1.38 specific gravity with two-fifths of its 
weight of water, and add solution of silver nitrate as long 
as a precipitate of silver chloride continues to form ; then 
add a further slight excess of solution of silver nitrate, let 
the precipitate subside, decant the perfectly clear super- 
natant acid into a retort or an alembic with ground head ; 
add some potassium nitrate free from chlorine, and distill 
until only a small quantity remains, taking care to attend 
to the proper cooling of the fumes distilling over. Dilute 
the distillate, if necessary, with water until it has a specific 
gravity of 1.2. 

Pure nitric acid must be colorless and leave no 
residue upon evaporation on platinum foil. Solution of 
silver nitrate or of barium nitrate must not cause the 
slightest turbidity in it. Dilute the acid with water before 
adding these reagents, as otherwise nitrates will pre- 
cipitate. Silver should be tested for by hydrochloric acid. 



NITROUS OXIDE. 
N 2 0. 

Five parts of stannous chloride, 10 parts of hydrochloric 
acid sp. gr. 1.2 1, and 0.9 part of nitric acid sp. gr. 1.38, 
are heated to boiling, when the evolution of nitrous oxide 
commences, and continues to be evolved quite regularly 
and in a pure state. The above proportions of ingredients 
should be adhered to, as otherwise the gas is evolved ir- 
regularly, and even with violent explosions.* 



* G. Campori, Ann. Chine. Pharm., 8, 253. 



20 LABORATORY MANUAL OF 

It can also be prepared from a mixture of ammonium 
sulphate and sodium nitrate, kept at 102 C. for 2 to 3 hours, 
undergoes in great part decomposition into sodium sulphate 
and ammonium nitrate. If, however, it is rapidly raised 
to a higher temperature, nitrous oxide begins to be evolved 
atno° C.,and comes off with some rapidity at 115 to 120 
C. During the heating up a little ammonia is evolved, and 
the longer the mixture is kept at about 104 to 1 io° C. the 
more ammonia is lost. If, then, the two salts have been mixed 
in molecular proportions, the deficiency in the ammonia 
leads to the evolution of some of the higher oxides of nitro- 
gen towards the end of the reaction. This may be remedied 
by increasing the proportion of ammonium sulphate, the 
mixture, with an additional 5 per cent, of that salt, affording 
a larger yield of nitrous oxide than would be obtained from 
the equivalent quantity of ammonium nitrate. The gas is 
evolved with regularity, whereas ammonium nitrate, raised 
to 1 1 5° C, decomposes with a rapidity, accelerating towards 
explosive violence.* 



NITRIC OXIDE. 
NO. 
A Woulff's bottle, fitted with a funnel and delivery 
tube, is filled loosely with strips of copper, and then one- 
third with a cold saturated solution of sodium nitrate. 
Strong sulphuric acid is added more or less quickly, ac- 
cording to the amount of gas required. The evolution of 
gas is very regular, and may be kept up for hours.f 



* By W. Smith, J. Soc. Chem. Ind., 11,867; *2, 10. 
f By H. Kaemmerer, Ber. 18, 3064-3066. 



INORGANIC PREPARATIONS. 21 

Nitric oxide may also be prepared from a mixture of 
solutions of potassium ferrocyanide and potassium nitrite 
added gradually from a stoppered funnel to a flask contain- 
ing acetic acid ; the contents of the flask must be vigor- 
ously shaken during the operation.* 

Another method is to add a strong solution of 
sodium nitrite to a solution of ferrous chloride or sulphate 
in hydrochloric acid. If the sodium nitrite contains car- 
bonate, it may be removed by precipitation with calcium 
chloride.f 

In order to obtain this gas in a very pure condition, the 
reaction which takes place in a Lunge's nitrometer is em- 
ployed; namely, treating mercury with a mixture of sul- 
phuric acid and nitric acid. The purity of the gas was placed 
beyond question by the results obtained on leading it over 
glowing copper ; the increase in weight of the metal, giv- 
ing the weight of oxygen, whilst the gas evolved, which 
was collected and measured, gave the weight of nitrogen. 
In the reaction between copper and nitric oxide, which 
is attended by the liberation of much heat, the metal is 
quantitatively converted into cuprous oxide.f 



NITROGEN TETRAOXIDE. 

N 3 4 . 

200 grams arsenious acid in pieces the size of a pea 

are placed in a tubulated retort with bent neck, 200 grams 

nitric acid 1.38 sp. gr. poured over it, and very moderately 



* By C. M. Van Deventer, Ber. 26, 589-593. 
f By J. Thiele, Annalen 253, 146. 
% By F. Enrich, Monatsh, 13, 73-77. 



22 LABORATORY MANUAL OF 

warmed. The evolved gas passes into an empty wash- 
bottle, is then dried by a tube filled with calcium nitrate 
and is finally conducted into a wide combustion-tube which 
is surrounded by a freezing mixture of ice and common salt 
A dark-green liquid condenses in this tube. Dry oxygen 
gas is conducted into it until the liquid has changed to 
a pure yellow, then the tube is sealed. 

The arsenic trioxide reduces the nitric acid passing 
into arsenic acid. In drying the gases calcium chloride 
must not be used, as they would be contaminated with 
chlorine, nor sulphuric acid, as it absorbs the gases. 
The condensed mixture of nitrogen trioxide and tetroxide 
is transformed by oxygen into pure tetroxide. 

The liquid should show a sp. gr. of 1.45 and boil at 
25 to 26° C. On cooling rapidly it should stiffen to a color- 
less crystal mass, which melts at about 12° C. 



SULPHURIC ACID. 
H 3 S0 4 or S0 2 (OH) 2 . 

a. Concentrated pure sulphuric acid. 

b. Concentrated sulphuric acid of commerce. 

c. Common dilute sulphuric acid. 

The following method may be recommended for pre- 
paring chemically pure sulphuric acid : 

a. Put 1,000 grams of ordinary concentrated sulphuric 
acid in a porcelain dish, and 3 grams of ammonium sul- 
phate, and heat till copious fumes of S0 3 begin to escape, 
in order to destroy the oxides of nitrogen which are 
present. After cooling, add 4 or 5 grams of powdered 
manganese dioxide, and heat to boiling with stirring, in 



INORGANIC PREPARATIONS. 23 

order to convert any arsenious acid into arsenic acid. 
When cool pour off the clear fluid by means of a long 
funnel tube into a retort coated with clay. The retort 
should not be more than half full, and is to be heated 
directly over charcoal. To prevent bumping, rest the 
retort on an inverted crucible cover, so that the sides may 
be more heated than the bottom. The neck of the retort 
must reach so far into the receiver that the acid, distilling 
over, drops directly into the body. To cool the receiver 
by means of water is unnecessary and even dangerous. 
To prevent the receiver from coming into actual contact 
with the hot neck of the retort, some asbestos in large 
fibres is placed between them. When about 10 or 15 
grams has been drawn over, change the receiver and slowly 
distil off three-fourths of the contents of the retort. This 
method depends upon the fact discovered by Bussy 
and Buignet, that on distilling sulphuric acid, which 
contains arsenic in the form of arsenic acid, an arsenic-free 
distillate is obtained. 

b. Pour into 4 parts of water 1 part of concentrated 
sulphuric acid, and conduct into the mixture for some time 
a slow stream of hydrogen sulphide, keeping the fluid 
heated to yo° C. Let the mixture stand at rest for several 
days, then decant the clear supernatant fluid from the 
precipitate, which consists of sulphur, lead sulphide, per- 
haps also arsenic sulphide, and heat the decanted fluid in a 
tubulated retort with upturned neck and open tubulature 
until sulphuric acid fumes escape with the aqueous 
vapor. The acid so purified is fit for many purposes 
of chemical analysis ; if it is desired, however, to free 
it also from non-volatile substances, it may be distilled 



24 LABORATORY MANUAL OF 

from a coated retort as in a. As soon as the drops in the 
neck of the retort become oily, the receiver is changed, 
and the concentrated acid which then passes over is kept 
in a separate vessel. 

c. Common dilute sulphuric acid. — Add to 5 parts of 
water in a thin glass or porcelain dish gradually, and whilst 
stirring, 1 part of concentrated sulphuric acid. The lead 
sulphate which seperates is allowed to subside, and the clear 
fluid finally decanted. 

Pure sulphuric acid must be colorless ; when color- 
less solution of ferrous sulphate is poured upon it in a 
test tube, no brown tint must mark the plane of contact 
of the two fluids (nitric acid, nitrous acid) ; when diluted 
with twenty parts of water it must not impart a blue tint 
to a solution of potassium iodide mixed with starch 
paste (nitrous acid). Mixed with pure zinc and water, 
it must yield hydrogen gas, which, on being passed 
through a red-hot tube, must not deposit the slightest 
trace of arsenic. It must leave no residue upon evapora- 
tion on platinum, and must remain perfectly clear upon 
dilution with four or five parts of alcohol (lead, iron, calcium). 
The presence of small quantities of lead is detected most 
easily by adding some hydrochloric acid to the sulphuric 
acid in a test tube. If the plane of contact is marked 
by turbidity (lead chloride), lead is present Sulphurous 
acid is discovered by the odor after shaking the acid in a 
half-filled bottle. 



INORGANIC PREPARATIONS. 



25 



HYDROGEN SULPHIDE. HYDROSULPHURIC 

ACID. SULPHURETTED HYDROGEN. 

H 3 S. 

Hydrogen sulphide is usually evolved from iron 
sulphide, which is broken into small lumps and then 
treated with dilute sulphuric or hydrochloric acid. Fused 
iron sulphide may be purchased cheaply, or may be made 
by heating iron turnings or 1 to 1 ^ inch iron nails, in a 
covered Hessian crucible to a white heat, and then adding 




Fig. 6. 

small lumps of roll-sulphur until the entire contents of the 
crucible are in fusion. As soon as this is the case, pour 
the fused mass upon sand, or into an old Hessian crucible. 
Or make a hole in the bottom of the crucible, when the 
iron sulphide will run through as fast as it forms, and may 



26 LABORATORY MANUAL OF 

be received in a shovel placed in the ash-pit. Or intro- 
duce an intimate mixture of thirty parts of iron filings and 
twenty-one parts of flowers of sulphur in small portions 
into a red-hot crucible, awaiting always the incandescence 
of the portion last introduced before proceeding to the 
addition of a fresh one. When you have thus put the 
mixture into the crucible, cover the latter closely, and 
expose it to a more intense heat, sufficient to make the 
iron sulphide fuse more or less, then allow the crucible to 
cool and break the sulphide in small pieces. 

The iron sulphide is then placed in a Kipp's apparatus, 
fig. 6, and the gas is generated by the action of dilute 
sulphuric or hydrochloric acids. 

HYDROGEN SULPHIDE FREE FROM ARSENIC. 

Calcium sulphide (prepared by igniting a mixture of 
plaster of Paris and coal) yields the pure gas when treated 
with dilute hydrochloric acid. To evolve the gas in a 
regular stream, a mixture of calcium sulphide, with one- 
fourth of its weight of plaster of Paris and enough water to 
make a cream, is poured into shallow paper trays. As 
soon as it has set, the cake is cut up into blocks, which 
are dried at a gentle heat. They may be used in Kipp's 
apparatus.* 

Another method is to use barium sulphate (powdered 
barytes) mixed with 25 per cent, of ground coal and 20 
per cent, of common salt. The dampened mixture is 
rammed into a clay crucible, which, after drying and 
closing with a luted cover, is heated for several hours 



* R. Fresenius, Zeit. Anal. Chem. 26, 339. 



INORGANIC PREPARATIONS. 2J 

at an incipient white heat. The product is in hard com- 
pact masses which dissolve completely in dilute hydro- 
chloric acid with a steady evolution of hydrogen sul- 
phide.* 

HYDROGEN SULPHIDE FREED FROM HYDROGEN 
ARSENIDE. 

This method is based on the fact that hydrogen arsen- 
ide reacts violently with iodine at ordinary temperature, 
arsenious iodide and hydrogen iodide being formed. 

A narrow tube, 30 to 40 cm. long, is loosely filled with 
coarsely powdered, air-dried iodine interspersed with glass 
wool ; 2 or 3 grams of iodine will remove every trace of ar- 
senic from hydrogen sulphide prepared from the ordinary 
impure materials, passing over it for several days. In 
purifying hydrogen, the latter is subsequently passed over 
glass wool wetted with potassium iodide solution and then 
through aqueous potash. t 

Free hydrogen sulphide in quantity is readily detected 
by its odor, and its blackening effect upon paper moist- 
ened with lead ajetate. 



SULPHUR DIOXIDE. 

so 3 . 

Prepared by gently heating in a flask scrap copper with 
concentrated, sulphuric acid 

Cu + 2H 2 S0 4 = S0 2 + 2H 2 + CuS0 4 . 
It can be absorbed in water and used as a solution of sul- 
phurous acid or absorbed in caustic alkalies forming 



* C. Winkler, Zeit. Anal. Chem. 27, 26. 
f O. Jacobsen, Ber. 20, 1999. 



28 LABORATORY MANUAL OF 

bisulphites which may be again used to generate sulphur 
dioxide by the action of cone, sulphuric acid. 

Prepared in this way, however, it is liable to contain 
sulphuric acid which is not readily removed. Sulphur 
dioxide is now obtainable in liquified condition and as 
such is used for disinfecting and freezing purposes. 

Sulphurous anhydride (S0 2 ) can be generated in 
Kipp's apparatus by the action of ordinary concentrated 
sulphuric acid on cubes prepared by Winkler's method 
from a mixture of 3 parts of calcium sulphite and 1 part of 
plaster. Economy in the use of cubes is effected if only 
the number required for the generation of the amount of 
gas needed are wetted with the acid at the commencement 
of the operation.* 

Sulphur Dioxide is recognized — 

1st. By its odor which is marked and well-known, re- 
sembling that of burning matches. 

2nd. Suspend in the gas a strip of paper which has 
been dipped into a solution of starch paste and potassium 
iodate. Iodine is liberated and the paper becomes blue. 
2KI0 3 + 5S0 3 + 4H 2 = 2HKS0 4 -f- 3H 2 S0 4 + I 2 . 



CARBON MONOXIDE. 
CO. 
Prepared by gently heating commercial oxalic acid in 
a capacious flask with cone, sulphuric acid. The acid 
exerts a dehydrating action and a mixture of carbon mon- 
oxide and carbon dioxide is evolved. The mixed gases are 



G. Neumann, Ber. 20, 1584. 



INORGANIC PREPARATIONS. 29 

passed through potassium hydrate solution which absorbs 
the carbon dioxide and sulphuric acid ; any water which 
may be present being removed by passing the gases 
through concentrated sulphuric acid. 

Another and better method is as follows : 
A mixture of finely powdered potassium ferrocyanide 
with eight or ten times its weight of cone, sulphuric acid is 
heated in a capacious flask ; the following reaction results: 
K 4 Fe(CN) 6 + 6H2SO4 + 6H 2 = 

6CO + 2K 2 S0 4 4- 3(NH 4 ) 3 S0 4 + FeS0 4 . 
If the heat is carefully regulated the evolution of gas is 
gentle and regular. The product, however, is liable to 
contain carbon dioxide and cyanogen compounds, hence it 
is better to wash with potassium hydrate. Carbon mon- 
oxide is recognized when in sufficient quantities by the 
bluish flame with which it burns. 



CARBON DIOXIDE. 
C0 2 . 

Prepared by treating coarsely broken marble with di- 
lute acids in Kipp's Apparatus, washed with water and dried 
over cone, sulphuric acid. It is used to remove chlorine in 
various operations where heat is undesireable. The gas 
may now be obtained in the liquid form, in steel cylin- 
ders and is used as a freezing agent. 

The free gas is detected by conducting it through a 
solution of calcium hydroxide, Ca(OH) 2 with which it 
forms a white precipitate (calcium carbonate). 

The free gas in water may be detected by adding the 
same solution as above. 



30 LABORATORY MANUAL OF 

SIMPLE AND RAPID PREPARATION OF PURE GASES. 

Instead of using an acid for the evolution of carbonic 
anhydride, sulphurous anhydride, and similar gases, it is 
convenient to use sodium hydrogen sulphate. A mixture 
of equivalent quantities of the respective salts in powder 
gives, when wetted with water, a regular stream of the re- 
quired gas, which will be free from the impurities usually 
derived from the use of an acid.* 



AMMONIA, 

NH, 

AMMONIUM HYDRATE. 
NH4OH. 

Prepared by gently heating crude ammonium sulphate 
with dry slaked lime 

2NH 4 C1 + Ca(OH) 3 = 2NH 3 + CaCI 2 4- 2H 3 

2NH 3 + 2H 2 = 2NH 4 OH. 

If gaseous ammonia is needed it must be caught by 
downward displacement of air, otherwise the gas is passed 
into water until saturated. 

To make ammonia for laboratory use the strongest 
ammonia water is dropped on porous calcium chloride, 
great heat is evolved during this operation but the gas 
which passes over is almost pure. 



* By H. Borntraeger, Zeit. Anal. Chem., 29, 140. 



INORGANIC PREPARATIONS. 3 I 



POTASSIUM HYDROXIDE, or POTASSA, 

KOH, 

and SODIUM HYDROXIDE, or SODA, 
NaOH. 

The preparation of perfectly pure potassa or soda is a 
difficult operation. It is advisable, therefore, to provide 
besides perfectly pure caustic alkali, some which is not 
quite pure, and some which, being free from certain im- 
purities, may in many cases be substituted for the pure sub- 
stance. 

a. Common solution of Soda. — Put into a clean cast-iron 
pan provided with a lid, 3 parts of crystallized sodium car- 
bonate of commerce and 1 5 parts of water, heat to boiling, 
and add, in small portions at a time, thick milk of lime pre- 
pared by pouring 3 parts of warm water over 1 part of 
fresh-burned quick-lime, and letting the mixture stand in 
a covered vessel until the lime is reduced to a uniform 
pulpy mass. Keep the liquid in the pan boiling while 
adding the milk of lime, for a quarter of an hour 
longer ; then filter off a small portion, and try whether the 
filtrate still causes effervescence in hydrochloric acid. If 
this is the case, the boiling must be continued, and if 
necessary some more milk of lime must be added to the 
fluid. When the solution is perfectly free from carbonic 
acid, cover the pan, allow the fluid to cool a little, and 
then draw off the nearly clear solution from the residuary 
sediment, by means of a siphon filled with water, and 



32 LABORATORY MANUAL OF 

transfer it to a glass flask. Boil the residue a second and 
third time with water, and draw off the fluid in the same 
way. Cover the flask close with a glass plate, and allow 
the lime suspended in the fluid to subside completely. 
Scour the iron pan clear, pour the clear solution back into 
it, and evaporate it to 6 or 7 parts. The solution so pre- 
pared contains from 9 to 10 per cent, of soda, and has 
a specific gravity of from 1.13 to 1.15. If it is wished to 
filter a solution of soda which is not quite clear, a cov- 
ered funnel should be used, which has been charged first 
with lumps of white marble and then with powder of the 
same, the fine dust being rinsed out with water before the 
filter is used (Graeger). Solution of soda must be clear, 
colorless, and as free as possible from carbonic acid ; am- 
monium sulphide must not impart a black color to it. 
Traces of silicic acid, alumina, and phosphoric acid are usu- 
ally found in a solution of soda prepared in this manner, 
on which account it is unfit for use in accurate experi- 
ments. Solution of soda is kept best in bottles closed with 
ground glass caps. In default of capped bottles, common 
ones with well-ground stoppers may be used, in which case 
the neck must be wiped perfectly dry and clean inside and 
the stopper coated with paraffine ; since, if this precaution 
is neglected, it will be found impossible after a time to 
remove the stopper, particularly if the bottle is only rarely 
opened. 

Absolutely pure soda is best prepared by dissolving 
sodium in pure water in a silver dish and evaporating un- 
til a drop of the liquid solidifies on cooling. 

The strength of the caustic soda solution is ascertained 
approximately by specific gravity. 



INORGANIC PREPARATIONS. 33 

% NaOH. Sp. Gr. % NaOH. Sp. Gr. 

10 I.I 1 5 21 1 .236 

11 1. 1 26 22 1-247 

12 1. 137 23 1.258 

13 1. 148 24 1.269 

14 i-i59 2 5 1 - 2 79 

15 1. 170 26 1.290 

16 1. 181 27 1 .300 

17 1. 192 28 1 .310 

18 1.202 29 1-321 

*9 X - 2I 3 3° 1 -33 2 

20 !-225 

The exact strength may be determined by titrating 
say 20 c. c. of the solution with normal acid, using phen- 
olphthalein as indicator, if any carbonic acid is present, a 
small quantity of barium chloride solution should be 
added before titrating. The calculation is very simple 
since 1 c. c. N/HC1 or N/2H 2 S0 4 = 0.040 gram. NaOH or 
0.0561 KOH. 

b. Potassa purified with alcohol. — Dissolve some caus- 
tic potassa of commerce in alcohol, in a stoppered bottle, 
by digestion and shaking ; let the fluid stand, decant it, or 
filter it if necessary, and evaporate the clear fluid in a sil- 
ver dish over the gas or spirit lamp until no more vapors 
escape, adding from time to time, during the evaporation, 
some water to prevent blackening of the mass. Place the 
silver dish in cold water until it has sufficiently cooled ; re- 
move the cake of potassa from the dish, break in coarse 
lumps in a hot mortar and keep in a well closed glass bot- 
tle. When required for use, dissolve a small lump in 
water. 



34 LABORATORY MANUAL OF 

The potassa so prepared is sufficiently pure for most 
purposes ; it contains a minute trace of alumina, but is 
usually free from phosphoric, sulphuric, and silicic acids. 
The solution must remain clear upon addition of ammonium 
sulphide ; hydrochloric acid must only produce a barely 
perceptible effervescence in it. The solution acidified with 
hydrochloric acid must, upon evaporation to dryness, leave 
a residue which dissolves in water to a clear fluid. The 
solution acidified with hydrochloric acid, and then mixed 
with ammonia in the least possible excess, must not show 
any flocks of alumina, at least until it has stood in a warm, 
place for several hours. The solution acidified with nitric 
acid must not give any precipitate with a nitric acid solu- 
tion of ammonium molybdate. 

Potassa prepared with baryta. — Dissolve pure crystals 
of baryta by heating with water, and add to the solution 
pure potassium sulphate until a portion of the filtered fluid, 
acidified with hydrochloric acid and diluted, no longer 
gives a precipitate on addition of a further quantity of the 
sulphate (16 parts of crystals of baryta require 9 parts of 
potassium sulphate). Let the turbid fluid clear, decant 
and evaporate in a silver dish. The potassa so prepared 
is perfectly pure, except that it contains a trifling admix- 
ture of potassium sulphate, which is left behind upon dis- 
solving in a little water. It is but rarely required, its use 
being in fact exclusively confined to the detection of 
minute traces of alumina, 



INORGANIC PREPARATIONS. 35 



BARIUM HYDROXIDE, or BARYTA. 

Ba(OH) 2 . 
There are many ways of preparing baryta; but 
as witherite (barium carbonate) is now cheaply procurable, 
the following method is preferable: Mix intimately to- 
gether ioo parts of finely pulverized witherite, 10 parts 
of charcoal in powder, and 5 parts of rosin, put the mix- 
ture in an earthenware crucible, lute on the lid with clay, 
and expose the crucible so prepared to the heat of a brick- 
kiln. Break and triturate the baked mass, boil repeatedly 
with water in an iron pot, filter into bottles, stopper, and 
let them stand in the cold, when large quantities of crystals 
of barium hydroxide Ba(OH) 3 + 8H 3 will make their 
appearance. Let the crystals drain in covered funnels, 
dry rapidly between sheets of blotting paper, and keep 
them in well closed bottles. For use, dissolve 1 part of the 
crystals in 20 parts of water, with the aid of heat, and filter 
the solution. The baryta water so prepared is purer than 
the mother liquor running off from the crystals. The res- 
idue, which is insoluble in water and consists of undecom- 
posed witherite and charcoal, may be turned to account in 
the preparation of barium chloride. 

Baryta water must, after precipitation of the barium 
by pure sulphuric acid, give a filtrate remaining clear when 
mixed with alcohol, and leaving no fixed residue upon 
evaporation in a platinum crucible. 

Barium hydroxide being a strong base, precipi- 
tates the metallic hydroxides insoluble in water from the 
solutions of their salts. 



$6 LABORATORY MANUAL OF 



CALCIUM HYDROXIDE, or LIME. 
Ca(OH) 2 . 

Calcium hydroxide is obtained by slacking lumps of 
pure calcined lime in a porcelain dish, with half their 
weight of water. The heat which accompanies the com- 
bination of the lime and the water is sufficient to evapor- 
ate the excess of water. Slacked lime must be kept in a 
well-stoppered bottle. 

To prepare lime water, digest slacked lime for some 
time with cold distilled water, shaking the mixture occa- 
sionally ; let the undissolved portion of lime subside, de- 
cant, and keep the clear fluid in a well-stoppered bottle. 
If it is wished to have the lime water quite free from all 
traces of alkalies, baryta and strontia, which are almost 
invariably present in slacked lime prepared from calcined 
limestone, the liquids of the first two or three decantations 
must be removed, and the fluid decanted afterwards alone 
made use of. 

Lime water must impart a strongly-marked brown 
tint to turmeric paper, and give a not too inconsider- 
able precipitate with sodium carbonate. It speedily loses 
these properties upon exposure to the air. 



LEAD DIOXIDE. 

Pb0 2 . 
a. In the dry way. 53 grams lead oxide are thor- 
oughly mixed in a mortar with 50 grams calcium carbonate, 
and a wide and not too deep clay crucible is filled loosely 



INORGANIC PREPARATIONS. 



37 



with the mixture and heated in Roessler's gas furnace (fig. 
7) for half an hour to fusion, regulating the draft so that 
there shall be an excess of air in the fusion chamber. 
After having cooled the slightly baked frit, it is powdered 




Fig. 7. 

in a mortar and once more heated for half an hour at a red 
heat. A powdered sample of the product is covered with 
diluted HN0 3 ; if carbonic acid is evolved, the powdered 
mass is to be heated a short while longer to white heat* 



* The oxydation goes on rapidly, if the mixture is heated in an infusi- 
ble clay dish (iron is impracticable, as it corrodes rapidly in Roessler's gas 
furnace at a high temperature). As soon as the mass begins to glow, stir 
vigorously with an iron spatula. During the process the small opening in 
the cover of the furnace is not closed. 



$8 LABORATORY MANUAL OF 

The finely powdered, flesh-colored calcium plumbate is 
poured gradually into 200 c. c. diluted HN0 3 ; after set- 
tling, it is decanted and ground in a mortar with fresh 
HNO3 (100 c. a). Finally it is once more boiled up with 
diluted HNO3, filtered, rinsed with hot water and dried on 
the waterbath. For most purposes it is more convenient 
to merely decant the peroxide with hot water and preserve 
it as paste. The weight of the lead peroxide obtained 
about equals that of the lead oxide taken.* 

b. In the wet way. A solution of 190 grams lead 
acetate in 500 c. c. water is placed into 500 c. c. of 20% 
soda lye and the cooled milky, alkaline solution treated by 
shaking with chlorine until no further precipitation takes 
place. It is then decanted with water and purified, as 
above, with nitric acid. 

By the aid of atmospheric oxygen and lead oxide, 
the carbonic acid of the calcium carbonate is expelled with 
formation of calcium plumbate corresponding with the ortho- 
silicates : 2CaC0 3 + PbO + O = Ca 3 Pb0 4 + 2C0 2 . The 
plumbate varying only very little in color from the original 
mixture, is easily decomposed with HN0 3 : Ca 2 Pb0 4 .+ 
4HN0 3 = 2Ca(N0 3 ) 3 + Pb0 3 4- 2H 3 0. 

In watery solution lead peroxide is formed through 
the action of chlorine on sodium lead oxide : Pb(ONa) 3 + 
2C1 = Pb0 3 + 2NaCl. 

The dark-brown lead peroxide, after being boiled with 
diluted HN0 3 , must not impart a violet color to the super- 
natant solution ; this color should appear immediately 
upon adding a drop of diluted manganese sulphate solu- 



* Kassner, Chem. Ind. 13, 1890, 104-120. 



INORGANIC PREPARATIONS. 39 

tion.* Suspended in diluted HN0 3 , it should dissolve 
readily and entirely upon addition of sodium nitrite. To 
determine the quantity of lead peroxide, an average sam- 
ple of the paste or the finely powdered preparation is 
weighed, placed into a flask with ground glass stopper, 
covered with diluted HN0 3 and gradually add a small ex- 
cess of normal sodium nitrite, aiding the reaction by fre- 
quent and vigorous shaking of the closed bottle. After all 
the peroxide has passed into solution, it is diluted with a 
large quantity of water and the excess of nitrite titrated 
back with potassium permanganate. 

Lead dioxide, when boiled with thrice its bulk 
of pure nitric acid for several minutes and allowed to 
settle, must not communicate the faintest red color to the 
acid (absence of manganese). 



LEAD CARBONATE. 
PbC0 3 . 

Lead oxide is readily converted into soluble hydroxide 
on treatment with a moderately concentrated solution of 
magnesium acetate. The solution thus obtained has an 
alkaline reaction, and yields lead carbonate when treated 
with carbonic anhydride. The white precipitate is col- 
lected, washed and dried, and the solution of magnesium 
acetate concentrated and used for another operation.f 



* Manganese protoxide is oxydized in nitric solution by lead peroxide 
into permanganic acid, Pb0 2 + HN0 2 + HN0 3 = Pb(N0 3 ) 2 + H 2 0. 
\ W. Kubel, Dingl. Polyt. J. 262. 143. 



40 LABORATORY MANUAL OF 



LEAD TETRACHLORIDE. 

Pb.ei 4 . 

When lead dichloride is suspended in hydrochloric acid 
and gaseous chlorine passed into the liquid, a solution of 
lead tetrachloride is obtained, from which, on addition of 
ammonium chloride, a compound, PbCl 3 NH 4 Cl, analogous 
to ammonium stanic chloride, separates. If this com- 
pound is added to concentrated sulphuric acid, an en- 
ergetic reaction ensues, and lead tetrachloride separates as 
an oily substance ; it is purified by shaking with fresh 
quantities of sulphuric acid. In the pure state, it is a 
translucent, yellow, highly refractive liquid which fumes 
in contact with moist air, with decomposition into lead 
dichloride and chlorine ; it may be kept under cold con- 
centrated sulphuric acid, but when heated with it, it de- 
composes with explosion into lead dichloride and chlorine. 
When, however, lead tetrachloride is heated in a retort 
with concentrated sulphuric acid, and a current of chlorine 
passes through, a certain quantity of the tetrachloride distils 
over below 105 ° C, at about which temperature explosion 
occurs. The sp. gr. of lead tetrachloride at o° C. is 3.18, 
and it solidifies to a yellowish crystalline mass at 15 C; it 
forms a hydrate in the presence of a little water, which, by 
the further addition of water, decomposes into lead perox- 
ide and hydrogen chloride ; when brought in contact with 
a small quantity of cooled hydrochloric acid, a crystalline 
derivative, probably PbCl 4 2HCl, is formed. 

* By H. Friedrich, Ber. 26, 1434-1436 ; compare Abetr. , 1890, 699 ; 
also Classen and Zahorski, Zeit. anorg. Chem. 4, 100. 



INORGANIC PREPARATIONS. 41 



BISMUTH HYDROXIDE. 
BiOOH. 
Dissolve bismuth, freed from arsenic by fusion with 
hepar sidphiiris, in dilute nitric acid ; dilute the solu- 
tion until a slight permanent precipitate is produced ; 
filter and evaporate the filtrate to crystallization. Wash 
the crystals with water containing nitric acid, triturate 
them with water, add ammonia in excess, and let the mix- 
ture digest for some time ; then filter, wash and dry the 
white precipitate. 

The bismuth hydroxide is dissolved in dilute nitric 
acid and precipitated with sulphuretted hydrogen. Part 
of the precipitated sulphide is treated with ammonia and 
filtered, and part treated with ammonium sulphide and 
filtered. The filtrates are then mixed with hydrochloric 
acid in excess ; the first should give no precipitate and the 
second only a white precipitate of sulphur. 



AMMONIUM SULPHIDE. 
a. Colorless ammonium monosulphide. (NH 4 ) 2 S. 

a. Transmit hydrogen sulphide through 3 parts of 
ammonia solution until no further absorption takes 
place; then add 2 parts more of the same ammonia 
solution. The action of hydrogen sulphide upon ammonia 
gives rise to the formation, first, of (NH 4 ) 3 S, (2NH 4 OH) 
and H 3 S = (NH 4 ) 2 S and 2(H 2 0)], then of NH 4 SH ; upon 
addition of the same quantitv of solution of ammonia as 



42 LABORATORY MANUAL OF 

has been saturated, the ammonia decomposes with the am- 
monium hydrosulphide and ammonium monosulphide is 
formed, thus: NH 4 SH -f NH 4 OH = (NH 4 ) 2 S + H 3 0. 
The rule, however, is to add only two-thirds of the quan- 
tity of solution of ammonia, as it is better the prepara- 
tion should contain a little ammonium hydrosulphide than 
that free ammonia should be present. To employ am- 
monium hydrosulphide instead of the simple monosulphide 
is unnecessary, and tends to increase the smell of sulphur- 
etted hydrogen in the laboratory, as the preparation al- 
lows that gas to escape when in contact with metallic acid 
sulphides. 

Ammonium sulphide should be kept in well- corked 
vials. It is colorless at first, and deposits no sulphur upon 
addition of acids. Upon exposure to the air, however, it 
acquires a yellow tint, owing to the formation of am- 
monium disulphide, which is attended also with formation 
of ammonia and water, thus: 2(NH 4 ) 3 S + O = (NH 4 ) 3 S 3 
+ 2NH 3 + H 3 0. Continued action of the oxygen of the 
air upon the ammonium sulphide tends at first to the for- 
mation of still higher sulphides ; but afterwards the fluid 
deposits sulphur, and finally all the ammonium sulphide is 
decomposed and the solution contains nothing but am- 
monia and ammonium thiosulphate. The formation of 
thiosulphate proceeds thus: (NH 4 ) 3 S 3 + 3 = (NH 4 ) 3 S 3 3 . 

b. Yellow ammonium polystdpJiide. (NH 4 ) 3 S X . 

b. The ammonium sulphide which has turned yellow 
by moderate exposure to the air may be used for all pur- 
poses requiring the employment of yellow ammonium 
sulphide. The yellow sulphide may also be expeditiously 
prepared by digesting the monosulphide with some sul- 



INORGANIC PREPARATIONS. 43 

phur. All kinds of yellow ammonium sulphide deposits 
sulphur and look turbid and milky on being mixed with 
acids. 

Ammonium sulphide must strongly emit the odor 
peculiar to it; with acids it must evolve abundance of 
sulphuretted hydrogen ; the evolution of gas may be 
attended by the separation of a pure white precipitate, but 
no other precipitate must be formed. Upon evaporation 
and exposure to a red heat in a platinum dish it must 
leave no residue. It must not, even on heating, precipi- 
tate or render turbid solution of magnesium sulphate or 
solution of calcium chloride (free ammonia, ammonium 
carbonate). 



SODIUM SULPHIDE. 

Na 2 S. 

POTASSIUM SULPHIDE. 
K 2 S. 

Preparation same as for ammonium sulphide, except 
that solutions of soda or potassa are substituted for the 
ammonia. Filter, if necessary, and keep the fluid obtained 
in well-stoppered bottles. If required to contain some 
higher sulphides, digest with powdered sulphur. 



AMMONIUM OXALATE. 

(NH 4 ) 2 CA, 2Aq. 
Dissolve commercial oxalic acid to saturation in hot 
hydrochloric acid of 10 to 12 per cent, cool rapidly 



44 LABORATORY MANUAL OF 

with constant agitation, wash the crystals (best with 
help of a filter pump) with cold water to remove 
most of the hydrochloric acid, redissolve in hot water, fil- 
ter hot to separate dirt, cool again with stirring, and wash 
the crystals with cold water until chlorine is mostly re- 
moved.* 

Dissolve the pure oxalic acid in 2 parts of distilled 
water, with the aid of heat, add solution of ammonia until 
the reaction is distinctly alkaline, and put the vessel in a 
cold place. Let the crystals drain. The mother liquor 
will, upon proper evaporation, give another crop of crys- 
tals. 

The solution of ammonium oxalate must not be 
precipitated nor rendered turbid by hydrogen sulphide, nor 
by ammonium sulphide. Ignited on platinum, the salt 
must volatilize without leaving a residue. 



SODIUM ACETATE. 
NaC 3 H 3 3 3Aq. 

Dissolve crystallized sodium carbonate in a little water, 
add to the solution acetic acid to slight excess, evaporate 
to crystallization, and purify the salt by recrystallization. 

Sodium acetate must be colorless and free from empy- 
reumatic matter and inorganic acids. 



* Stolba. 



INORGANIC PREPARATIONS. 45 



PURE SODIUM CHLORIDE. 

NaCl. 

500 grams common salt and 1500 c. c. cold water are 
ground together in a mortar holding 3 litres, filtered 
through a folded filter into a porcelain dish of about 3 litres 
capacity and heated on a gas stove. Now add milk of lime 
prepared from 5 grams caustic lime and mix with barium 
chloride solution in small excess. After settling, it is 
filtered into a beaker and the clear fluid precipitated with 
soda solution (prepared from 1 5 grams pure, dry sodium car- 
bonate). The filtrate is neutralized at a boiling heat with 
dilute hydrochloric acid (about 25 c. c.) and as quickly as 
possible evaporated over a large burner to y 2 litre. The 
separated sodium chloride is collected on a funnel fitted with 
a platinum cone, sucked dry with the filter pump and the 
salt further dried by warming in a platinum or porcelain 
dish, stirring constantly with a platinum spatula or glass rod. 

The magnesium and iron contained in the common 
salt are precipitated by the calcium hydrate as hydroxides. 
MgCl 2 + Ca(OH) 2 = Mg(OH) 2 + CaCl 3 . 

The sulphuric acid precipitated by the barium chloride. 
CaS0 4 + BaCl 3 = BaS0 4 4- CaCl 3 . 

The alkaline earths finally separated as carbonates. 
CaCl 3 + Na 2 C0 3 = CaC0 3 + 2NaCl. 

Sodium chloride forms a snow-white crystalline powder 
consisting of small squares. The dried salt warmed 
in small dry tubes should not decrepitate ; and at a 



46 LABORATORY MANUAL OF 

higher temperature it should melt to a perfect liquid. The 
watery solution should be examined with ammonium oxa- 
late, sodium phosphate, potassium ferrocyanide and barium 
chloride for presence of calcium, magnesia, iron and sul- 
phuric acid. One drop of the solution with ten drops 
platinum chloride evaporated to a small volume on a 
watch-glass yields upon cooling nice triclinic prisms of so- 
dium platinic chloride, Na 3 PtCl 6 4- 6Aq, which, on solution 
in alcohol, must not leave any residue of potassium platinic 
chloride.* 



SODIUM. 



Sodium, which when kept under mineral oil has be- 
come covered with a crust, is easily purified by immersing 
in a mixture of amyl alcohol (i part) and petroleum (3 
parts) and rubbing with a rag soaked in the same mixture 
until it acquires a silvery lustre. It is then laid in petro- 
leum containing 5 per cent, of amyl alcohol, washed with 
pure petroleum and kept in petroleum containing 0.5 to 1 
per cent, of amyl alcohol. The bright metal becomes 
slowly covered with a film of sodium of amyloxide, which 
is, however, easily rubbed off with filter paper. Potassium 
and lithium can be purified in the same way and thus 
keep their metallic lustre for a long time. 



* On an average 12 g. crystallized barium chloride are used. As the 
conclusion of the reaction is only recognized with difficulty, in the muddy 
solution, you can take here, as in many other cases, conveniently small 
samples from the top of the liquid by dipping in a fine capillary tube. The 
capillary is blown out on to a watch-glass. In the present case the watch- 
glass is placed on a black support and tested with a drop of BaCl 2 solution, 
which will form BaS0 4 if H 2 S0 4 be present. 



INORGANIC PREPARATIONS. 47 

Sodium cleaned, as above, combines at once with mer- 
cury with evolution of light. The liquid alloy of sodium 
and potassium is easily prepared by pressing together the 
two clean metals under a mixture of amyl alcohol (I part), 
and petroleum (9 parts). Sodium sulphide is also easily 
prepared by rubbing the clean metal (1 gram) and salt 3 
grams) to a fine powder, and then mixing with sulphur 
(0.7 gram), care being taken to avoid any pressure. When 
the two substances are intimately mixed, combination sud- 
denly takes place with evolution of light. If the mixture 
of sodium powder and salt be mixed with sulphur in the 
proportions required to form the di- or tri-sulphide, the re- 
action takes place more quickly and violently. 

Selenium and tellurium behave in the same way as sul- 
phur when mixed with sodium powder.* 



SODIUM AMALGAM. 

(10%). 

Heat 3 kilos of mercury in a covered iron pot and 
gradually add 300 grams of sodium, in pieces of about 
5 grams each. On the addition of each piece of 
sodium there is a violent action; toward the close of the 
operation it is usually necessary to increase the heat and 
stir the mass to produce this reaction. It is not advisable 
to clean the sodium, as the oxide is reduced during the 
operation and loss avoided. (During the operation glasses 
should be worn to protect the eyes.) 



By M. Rosenfeld, Ber. 24, 1658. 



48 LABORATORY MANUAL OF 

When no further reaction takes place after stirring, the 
melted mass is poured out on a clean iron plate, broken as 
soon as solid and while still warm, packed in small tightly 
closing glass-stoppered bottles. 

Sodium Amalgam is used as a means of generating 
small quantities of hydrogen for reducing purposes. (See 
Hydrogen, page 9). 



SODIUM CARBONATE. 

(Na 2 CO 3 10Aq.) 

It is best to provide this salt in several grades of 
purity, as follows: 

a. Free from sulphur and chlorine. Finely pulverize 
" bicarbonate of soda " of commerce, put the powder into 
a funnel stopped loosely with some cotton, make the sur- 
face even, cover it with a disk of thick filter paper with 
turned-up edges, and wash by pouring small quantities of 
water on the paper disk until the filtrate, when acidified 
with nitric acid, is not rendered turbid by solution of silver 
nitrate, nor by solution of barium chloride. Let the salt 
dry, and then convert it by gentle ignition into the simple 
carbonate. This is effected best in a vessel of silver or 
platinum ; but it may be done also in a perfectly clean 
iron, or, on a small scale, in a porcelain dish. 

b. Free from silica. The salt, as prepared in a, is liable 
to contain silica as well as sand and dirt. To purify it 
further, dissolve in twice its weight of water, or dissolve 
" sal soda " crystals in their own weight of water, filter, and 
pass into the cold solution washed pure carbon dioxide, 
but not to complete saturation. 



INORGANIC PREPARATIONS. 49 

The crystals of hydrogen sodium carbonate that sep- 
arate are drained in a funnel, washed with cold water, 
dried, and gently ignited, as above directed, as long as 
water is given off. Prepared in glass vessels by this 
method, sodium carbonate may be readily procured con- 
taining but fcioo of silica. 

c. To a clear and cold solution of 145 grams of sal 
soda crystals in 100 c. c. of water, add gradually with vig- 
orous stirring a solution of 60 parts of purified oxalic acid 
in 100 c. c. of warm water. When sodium oxalate ceases 
to separate, break up the crystals, and transfer them to a 
6-inch filter connected with the Bunsen filter pump, wash 
with 500 c. c. of water and dry. Heat to full redness in a 
platinum dish until the oxalate is fully decomposed, dis- 
solve, filter, and evaporate to dryness.* 

Sodium carbonate must be perfectly white. Several 
grams of the salt must dissolve in water without turbid- 
ity, and if the salt is to be used in a flux, without leav- 
ing grains of sand. Its solution, after supersaturation 
with nitric acid, must not be rendered turbid by ba- 
rium chloride or silver nitrate ; nor must addition of potas- 
sium sulphocyanate impart a red, or warming with 
ammonium molybdate and nitric acid a yellow tint to it, 
or give a yellow precipitate ; the residue which remains 
upon evaporating its solution to dryness, after previous 
supersaturation with hydrochloric acid, must leave no resi- 
due (silica) when redissolved in water. When fused in a 
glass tube with potassium cyanide for a long time in a cur- 
rent of carbon dioxide, it should give no trace of a dark 
sublimate (arsenic). 

* J. Lawrence Smith. 



5<D LABORATORY MANUAL OF 



POTASSIUM CYANIDE. 
KCN. 

Heat potassium ferrocyanide of commerce (perfectly- 
free from potassium sulphate) gently, with stirring, 
until the crystallization water is completely expelled ; 
triturate the anhydrous mass, and mix 8 parts of the 
dry powder with 3 parts of perfectly dry potassium car- 
bonate ; fuse the mixture in a covered Hessian, or, bet- 
ter still, in a covered iron crucible, until the mass is in a 
faint glow, appears clear, and a sample of it, taken out 
with a heated glass or iron rod, looks perfectly white. 
Remove the crucible now from the fire, tap it gently, and 
let it cool a little until the evolution of gas has ceased ; 
pour the fused potassium cyanide into a heated, tall, 
crucible-shaped vessel of clean iron or silver, or into a 
moderately hot Hessian crucible, with proper care, to pre- 
vent the running-out of any of the minute particles of iron 
which have separated in the process of fusion and have 
subsided to the bottom of the crucible. Let the mass 
now slowly cool in a somewhat warm place. The potas- 
sium cyanide so prepared is exceedingly well adapted for 
analytical purposes, although it contains potassium car- 
bonate and cyanite, which latter is upon solution in water 
transformed into ammonium carbonate and potassium car- 
bonate (2CNOK + 4H 3 = K 2 C0 3 + (NH 4 ) 3 C0 3 ). Keep 
it in the solid form in a well-stoppered bottle. 

Potassium cyanide must be of a milk-white color 
and quite free from particles of iron or charcoal. It 
must completely dissolve in water to a clear fluid. It 



INORGANIC PREPARATIONS. 5 I 

must contain neither silica nor potassium sulphide; the 
precipitate which lead salts produce in its solution must 
accordingly be of a white color, and the residue which 
its solution leaves upon evaporation, after previous super- 
saturation with hydrochloric acid, must completely dissolve 
in water to a clear fluid. 



POTASSIUM SULPHOCYANIDE. 

KCNS. 

Mix together 46 parts of anhydrous potassium 
ferrocyanide, 17 parts of potassium carbonate, and 32 
parts of sulphur; introduce the mixture into an iron 
pan provided with a lid, and fuse over a gentle fire ; 
maintain the same temperature until the swelling of the 
mass which ensues at first has completely subsided and 
given place to a state of tranquil and clear fusion ; in- 
crease the temperature now towards the end of the opera- 
tion, to faint redness, in order to decompose the potas- 
sium thiosulphate which has been formed in the process. 
Remove the half-cooled and still soft mass from the 
pan, crush it, and boil repeatedly with alcohol of from 
80 to 90 per cent. Upon cooling, part of the potassium 
sulphocyanide will separate in colorless crystals ; to obtain 
the remainder, distil the alcohol from the mother liquor. 

Solution of potassium sulphocyanide must remain 
perfectly colorless when mixed with perfectly pure dilute 
hydrochloric acid. 



52 LABORATORY MANUAL OF 



HYDROGEN SODIUM SULPHITE. 
HNaS0 3 . 

Heat 5 parts of copper tacks or clippings with 
20 parts of concentrated sulphuric acid in a flask, 
and conduct the sulphur dioxide gas evolved, first 
through a washing bottle containing some water, then 
into a flask containing 7 parts of clean crystallized sal- 
soda, and from 20 to 30 parts of water, and which is 
not much more than half full ; continue the transmission 
of the gas until the evolution of carbon dioxide ceases. 
Keep the solution, which smells strongly of sulphurous 
acid, in a well-stoppered bottle. 

Acid sodium sulphite, when evaporated to dryness 
with pure sulphuric acid, must leave a residue, the aque- 
ous solution of which is not altered by hydrogen sulphide, 
nor precipitated yellow by heating with a solution of 
ammonium molybdate mixed with nitric acid. 



POTASSIUM NITRITE, 
KN0 3 . 

In an iron pan fuse 1 part of nitre, add 2 parts 
of lead, and keep stirred with an iron rod. Even 
at a low red heat the lead becomes for the most 
part oxidized and converted into a yellow powder To 
oxidize the remainder, the heat is increased to visible 
redness and maintained at that point for half an hour 
Allow to cool, treat with cold water, filter and pass car- 



INORGANIC PREPARATIONS. 53 

bon dioxide through the filtrate. This precipitates al- 
most the whole of the lead in solution, the remainder is 
removed with a little hydrogen sulphide. Evaporate the 
clear fluid to dryness, finally with stirring, and fuse in 
order to destroy any potassium thiosulphate. — (Aug. 
Stromeyer.) When required, dissolve I part in 2 parts 
of water, neutralize cautiously with acetic acid, and filter. 

Potassium nitrite must, upon addition of dilute sul- 
phuric acid, copiously evolve nitrogen dioxide gas. 



SODIUM AND POTASSIUM NITRITE. 

A very sensitive surface of spongy platinum is ob- 
tained by soaking asbestos yarn in a solution of platinum 
oxalate, made by heating freshly prepared platinic chloride 
at 204 C, until no more chlorine is evolved, then boiling 
the residue with a slight excess of sodium carbonate, 
finally dissolving it in oxalic acid, and concentrating the 
solution. The soaked asbestos yarn, after drying and 
igniting, is exposed to a current of ammonia and air in a 
combustion tube, the remote end being heated by a Bun- 
sen burner to start the reaction ; the whole platinized sur- 
face soon becomes intensely hot, while dense clouds of 
ammonium nitrite rapidly form, and are conducted into 
sodium or potassium hydroxide, where the corresponding 
nitrite is formed, the evolved ammonia being used for pro- 
ducing a further supply of ammonium nitrite,* 



By H. N. Warren, (Chem. News, 63, 294). 



54 LABORATORY MANUAL OF 



POTASSIUM PYROANTIMONATE. 
HgKgSbgOyGHgO. 

Introduce a mixture of equal parts of pulverized 
tartar-emetic and potassium nitrate in small portions 
at a time into a red-hot crucible. After the mass 
has deflagrated, keep it at a moderate red heat for a quar- 
ter of an hour ; it froths at first, but after some time it will 
be in a state of calm fusion. Remove the crucible from 
the fire, let the mass get nearly cold, and extract it 
with warm water. Transfer to a suitable vessel, by rinsing, 
and decant the clear fluid from the heavy white powder 
deposited. Concentrate the decanted fluid by evaporation. 
After one or two days a doughy mass will separate. Treat 
this mass with three times its volume of cold water, work- 
ing it at the same time with a spatula. This operation will 
serve to convert it into a fine granular powder, to which 
add the powder from which the fluid was decanted, wash 
well with boiling water, till the washings cease to be alka- 
line, and dry on blotting paper, ioo parts of tartar-emetic 
give about 36 parts of the pyroantimonate Brunner). 



AMMONIUM MOLYBDATE. 

( (NH 4 ) 2 Mo0 4 , 

Dissolved in Nitric Acid. 

Molybdic Solution. 

Triturate molybdenum sulphide with about an equal 

bulk of coarse quartz sand washed with hydrochloric 

acid, until it is reduced to a moderately fine pow- 



INORGANIC PREPARATIONS. 55 

der ; heat to faint redness, with repeated stirring, until 
the mass has acquired a lemon-yellow color (which after 
cooling turns whitish). With small quantities this opera- 
tion may be conducted in a flat platinum dish, with large 
quantities in a muffle. Extract with solution of ammonia, 
filter, evaporate the filtrate, heat the residue to faint red- 
ness until it appears yellow or white, and then digest for 
several days with nitric acid in the water bath, in order to 
convert any phosphoric acid present to the tribasic state. 
When the nitric acid is evaporated dissolve the residue in 
4 parts of solution of ammonia, filter rapidly, and pour the 
filtrate into 15 parts by weight of nitric acid of 1.20 specific 
gravity. Keep the mixture standing several days in a 
moderately warm place, which will cause the separation of 
any remaining traces of phosphoric acid as ammonium 
phosphomolybdate. Decant the colorless fluid from the 
precipitate, and keep it for use. Heated to 40 C. no white 
precipitate (molybdic acid or an acid salt of the same) will 
separate ; but above that point precipitation will take place 
unless more nitric acid be added (Eggertz). 



AMMONIUM CHLORIDE. 
NH4CI. 

Select sublimed white sal ammoniac of commerce. 
If it contains iron it must be purified by slowly pass- 
ing chlorine gas into the nearly saturated solution for a 
short time or until potassium ferricyanide gives no blue 
color with a few drops of the liquid. Ammonia is then 
added in slight excess, the whole is warmed, filtered from 
the separated ferric oxide and evaporated to crystallization. 



56 LABORATORY MANUAL OF 

Solution of Ammonium Chloride must leave no fixed 
residue upon evaporation on platinum, and ammonium 
sulphide must have no action upon it. Its reaction must 
be perfectly neutral. 



SODIUM NITRATE. 
NaN0 3 . 
Neutralize pure nitric acid with pure sodium car- 
bonate exactly, and evaporate to crystallization. Dry the 
crystals thoroughly, triturate and keep the powder for use. 
A solution of sodium nitrate must not be made turbid 
by solution of silver nitrate or barium nitrate, nor precipi- 
tated by sodium carbonate. 



MONO SODIUM PHOSPHITE. 
2NaHP0 3 + 5H 3 0. 
Is obtained by adding sodium hydroxide or carbonate 
to phosphorous acid until the solution is neutral to methyl 
orange. The liquid is then concentrated by evaporation 
and the salt crystallizes. Not unfrequently a supersatur- 
ated solution is obtained, which crystallizes in contact 
with a fragment of the solid phosphite. If no crystals of 
the phosphite are at hand, the solution is concentrated un- 
til it has the composition of the crystals and is cooled to a 
low temperature. The salt is recrystallized from water 
and dried by exposure to air. It can also be obtained by 
the action of phosphorus trichloride on sodium carbonate, 
but the separation of the sodium chloride is difficult. 



INORGANIC PREPARATIONS. 57 

Monosodium phosphite is very soluble in water and melts 
at 42 C. At ioo° C. the fused salt loses water and the 
liquid deposits crystals which may be either a lower 
hydrate or the anhydrous salt. If heated at ioo Q C. for 
a long time, it becomes completely dehydrated ; it also 
becomes anhydrous in a dry vacuum. When heated 
above 130 C. the phosphite changes into sodium pyro- 
phosphate. 

Potassium phosphite is obtained in a similar manner. 
It forms anhydrous crystals, which are difficult to purify by 
recrystallization. 



POTASSIUM CHLORATE. 
KCIO3. 

100 grams potassium carbonate are dissolved in warm 
water in a small flask heated to boiling, and chlorine is 
conducted through the liquid until it is no longer alkaline. 
Then dilute with hot water up to a volume of 350 c. c, fil- 
ter and let it crystallize. 

As a test a weighed sample of the dried salt put in a 
covered platinum dish is heated first on the gas furnace, 
then on the Bunsen burner with a small flame to incipient 
redness ; the uncovering of the hot dish must be avoided. 

3K 2 C0 3 + 6C1 = KCIO3 + 5KC1 + 3C0 3 . 

The potassium chloride remains in the mother liquor. On 
heating the potassium chlorate, the perchlorate first forms, 
then the chloride and this finally volatilizes at red heat. 



58 LABORATORY MANUAL OF 



POTASSIUM BISULPHATE. 
KHSO4. 

Mix 7 parts of pure sodium sulphate (obtained by 
recrystallization of clean Glauber's salts, and drying away 
the water of crystallization at a gentle heat) with 5 parts 
of pure concentrated sulphuric acid, in a platinum dish or 
large platinum crucible, heat to low redness till the mass 
is in a state of calm fusion, then pour out into a platinum 
dish placed in cold water, or upon a piece of porcelain, 
break the cake into smaller pieces and keep for use. 

The sodium disulphate must dissolve in water with 
ease to a clear fluid with a strong acid reaction. The 
solution must not be rendered turbid or precipitated by 
hydrogen sulphide or by ammonia and ammonium sul- 
phide. 



HYDROGEN SODIUM AMMONIUM PHOSPHATE. 
NaHNH 4 P0 4 . 

a. Heat to boiling 6 parts of hydrogen disodium 
phosphate and 1 part of pure ammonium chloride with 2 
parts of water, and let the solution cool. Free the crys- 
tals produced, from the sodium chloride which adheres to 
them, by recrystallization, with addition of some solution 
of ammonia. Dry the purified crystals, pulverize and keep 
for use. 

b. Take 2 equal parts of pure tribasic phosphoric acid, 
and add solution of soda to the one, solution of ammonia 



INORGANIC PREPARATIONS. 59 

to the other, until both fluids have a distinct alkaline reac- 
tion ; mix the two together, and let the mixture crystal- 
lize. 

Hydrogen sodium ammonium phosphate dissolves 
in water to a fluid with feebly alkaline reaction. The 
yellow precipitate produced in this fluid by silver ni- 
trate must completely dissolve in nitric acid. Upon fusion 
on a platinum wire, microcosmic salt must give a clear and 
colorless bead. 



POTASSIUM FERRICYANIDE. 

K 6 Fe 2 Cyi 2 . 

Conduct chlorine gas slowly into a solution of I part 
of potassium ferrocyanide in 10 parts of water, with 
frequent stirring, until the solution exhibits a fine deep 
red color by transmitted light (the light of a candle 
answers best), and a portion of the fluid produces no 
longer a blue precipitate in a solution of ferric chloride, 
but imparts a brownish tint to it. Evaporate the fluid now 
in a dish to y^ of its weight, and let crystallize. The 
mother liquor will upon further evaporation yield a second 
crop of crystals equally fit for use as the first. Dissolve 
the whole of the crystals obtained in 3 parts of water, filter 
if necessary ; evaporate the solution briskly to half its vol- 
ume, and let crystallize again. The solution, as already 
remarked, must produce neither a blue precipitate nor a 
blue color in a solution of ferric chloride. As this salt de- 
composes when long kept in solution, it is best preserved 
and applied in the state of powder. 



6o LABORATORY MANUAL OF 



POTASSIUM IODIDE. 
KL 

6 grams pure iron powder are suspended in a small flask 
with 50 c. c. water, 25 grams iodine are gradually added, 
keeping the mixture cold. At the end of the reaction there 
must still be present a slight excess of iron. The solution 
is filtered off from the residue, washed with a little water, 
and 5 grams iodine added to the filtrate. Now 16.5 grams 
potassium carbonate are dissolved in a porcelain dish with 
50 c. c. hot water, and the ferrous iodide solution added to 
this boiling mixture. Ferrous h)^drate separates and car- 
bonic acid is freely evolved ; filter and evaporate to crystall- 
ization. 

By the above process a mixture of ferrous and ferric 
iodides is formed, and this by decomposition with alkali 
yields ferrous oxide, which is readily removed by filtration. 

The potassium iodide in sulphuric acid solution must 
not turn starched paper blue, and must be free from 
bromine and chlorine. 



POTASSIUM CYANATE. 
KCNO. 
Commercial potassium ferrocyanide is broken in pieces, 
dehydrated in an iron dish on a gas furnace and finely 
powdered. 200 grams of the anhydrous salt are thor- 
oughly mixed with 150 grams potassium dichromate which 
has been freed from adhering moisture by fusing on the 



INORGANIC PREPARATIONS. 6 1 

gas stove. The mixture is placed into a capacious iron 
dish in portions by means of a spoon, and heated to such 
an extent over a Bunsen burner or gas stove that every 
portion of the powder added is converted into a black 
mass. Stir with an iron spatula while putting the mixture 
into the dish. The temperature must not rise high enough 
to cause fusion of the mass. After cooling, the porous 
mass is powdered, put into a flask with I litre of 80% 
boiling alcohol, shaken and boiled for five minutes, 
with reversed condenser. After settling, pour off the clear 
solution into a beaker, which is set in cold water to cool, 
whereupon the potassium cyanate, especially by stirring 
with a glass rod, precipitates in a heavy white crystallized 
powder. The mother liquor serves for further (3d or 4th) 
extraction of the black product. 

K 4 Fe(CN) 6 +2K 2 Cr 2 7 = 6KCNO + 2Cr 2 3 + FeO + K 2 0. 

The unaltered potassium ferrocyanide remains in- 
soluble on recrystallization from alcohol. The hot 
solutions must be cooled quickly, as by heating any length 
of time, the water contained in the diluted alcohol would 
decompose the cyanate. 

KCNO + 2H 2 = K(NH 4 )C0 3 . 

Analyze the salt by evaporating a sample with cone, 
sulphuric acid and fusing the remaining potassium sul- 
phate with addition of a grain of ammonium carbonate.* 



* C. A. Bell, Chem. News, 32, 99. 



62 LABORATORY MANUAL OF 



POTASSIUM COBALTIC OXALATE. 

K 6 Co 2 (C 3 4 ) 6 + 6H 3 0. 

Is obtained by mixing cobaltic hydroxide, potassium 
oxalate, oxalic acid and water to a thick paste, and allow- 
ing the mixture to stand from 1 4to 2 1 days. After recrystall- 
ization, the salt is obtained in nearly black, well-formed, 
seemingly monosymmetric crystals, which in thin lamellae 
show distinct dichroism (dark-blue and emerald-green).* 

When treated with cold saturated sodium chloride solu- 
tion, the sodium potassium salt is obtained, crystallizing in 
beautiful pyramids. 



POTASSIUM METANTIMONATE. 

K 4 Sb 3 O r . 
100 grams of black sulphide of antimony, 150 grams of 
potassium carbonate, IOO grams of slaked lime and 20 
grams of sulphur, are shaken with 12 liters of water and 
after standing eight days the mixture is filtered. The fil- 
trate, which contains potassium sulphantimonate, is boiled 
with 120 grams of copper oxide and filtered. The filtrate 
is diluted with water and treated with carbonic anhydride, 
when potassium metantimonate is precipitated.! 



* F. Kehrmann, Ber., 19, 3101. 

f Duyk, Bull. Soc. Roy. Pharm., Bruxelles, 37, 109. 



INORGANIC PREPARATIONS. 6$ 

CRYSTALLINE NORMAL LITHIUM PHOS- 
PHATE and ARSENATE. 

Fused lithium chloride dissolves the amorphous, normal 
phosphate, and on cooling and washing the melted mass, 
rhomboidal, tabular crystals of normal lithium phosphate, 
which have a sp. gr. 2.41 at 15 C, and are infusible at a 
white heat, are obtained. The normal arsenate is similarly 
prepared ; it corresponds with the phosphate physically, 
and is of sp. gr. 3.07 at 15 C* 



PREPARATION OF PURE CAESIUM AND 
RUBIDIUM COMPOUNDS 

The preparation of pure caesium rubidium salts from 
their minerals is carried out as follows : They are first 
separated in the form of the double salts with lead tetra- 
chloride ; the latter is decomposed with water, the solu- 
tion treated with a slight excess of ammonium sulphide to 
free it from lead, and the filtrate evaporated to dryness ; 
the mixed chlorides of caesium and rubidium are dissolved 
in concentrated nitric acid, the solution evaporated to dry- 
ness, the residue dissolved in water, excess of oxalic acid 
added, and the mixture again evaporated to dryness, and 
heated in a platinum crucible until the oxalates are com- 
pletely converted into carbonates. The rubidium is then 
separated as acid oxalate and the caesium as caesium anti- 
mony chloride, t 



* By A. de Shulten, Bull. Soc. Chim. [3], 1, 479. 
f By H. L. Wells, Amer. J. Sci., 46, 186. 



64 LABORATORY MANUAL OF 



PREPARATION OF PURE RUBIDIUM SALTS. 

Commercial " pure " rubidium salts contain small quan- 
tities of caesium and potassium, which it is difficult to detect 
by means of the spectroscope. To obtain a pure salt, com- 
mercial rubidium chloride (30 grams) is dissolved in very 
strong hydrochloric acid (250 c. c.) and antimony chloride 
(2.5 grams) dissolved in strong hydrochloric acid is added. 
The small precipitate (about 1.4 grams Rb, SbCl^ and 
CsSbCl 4 ) is filtered off on an asbestos filter, the filtrate 
evaporated almost to dryness, the antimony still present 
removed with hydrogen sulphide, and the resulting mix- 
ture dissolved in strong hydrochloric acid. Rather more 
of a hydrochloric acid solution of stannic chloride is added 
than is necessary to form the stannic chloride, Rb 3 SnCl 6 ; 
this substance is then precipitated, whilst potassium stannic 
chloride, K 3 SnCl 6 , remains in solution. The precipitate is 
allowed to settle, washed several times by decantation, col- 
lected on an asbestos filter, dissolved in water, and the tin 
removed with hydrogen sulphide. The rubidium chloride 
so obtained is pure, 0.44 gram contains 29.30 instead of 
29.34 per cent, of chlorine.* 



PREPARATION OF TUNGSTATES FREE 
FROM MOLYBDENUM. 

Commercial tungstates and tungstic acid contain vary- 
ing quantities of molybdenum. After several unsuccessful 
attempts to get rid of this impurity, the following method 



By W. Muthmann, Ber. 26, 1019-1020. 



INORGANIC PREPARATIONS. 65 

was found to give the desired result. Sodium tungstate, 
prepared in the usual way, is dissolved in cold water, and 
to the saturated solution hydrochloric acid is added until 
the reaction is only feebly alkaline ; the paratungstate thus 
obtained is crystallized out and once recrystallized. One- 
half of it is dissolved in boiling water, and hydrochloric 
and a little nitric acid added ; hydrated tungstic acid is 
precipitated. This is washed thoroughly with hot water 
and added to a boiling solution of the other half of the 
paratungstate, until a portion no longer gives a precipi- 
tate with hydrochloric acid. The bulk of the solution is 
then filtered, hydrochloric acid is added, and the solution 
is boiled and repeatedly saturated with hydrogen sulphide. 
This precipitates the molybdeum as sulphide, whilst the 
metatungstate is not attacked. The solution is filtered, 
concentrated, oxidized with a few drops of bromine water, 
and neutralized with soda ; pure sodium paratungstate 
can then be obtained from it by crystallization. To ob- 
tain the potassium and ammonium salts, the acid should be 
prepared by adding hydrochloric acid to the sodium salt, 
and then neutralize with potash or ammonia. 

An analysis of sodium paratungstate thus prepared 
agreed better with the formula 5Na 3 0, 12W0 3 , 28H 3 
than with 3Na 2 0, 7W0 3 , 16H 2 0.* 



TITANIUM TRIOXIDE. 
T1O3. 
Pure titanium chloride is added drop by drop to dilute 
alcohol, and the clear and very dilute solution is treated 



* By C. Friedheim and R. Meyer, Zeit. Anorg. Chem. i, 76-81. 

5 



66 LABORATORY MANUAL OF 

with a large excess of hydrogen peroxide. Ammonia, am- 
monium carbonate, or aqueous potash, is added to the 
solution with the production of a yellow, or in case of 
ammonia, of a reddish yellow liquid, which after some time 
yields a yellow precipitate. This is allowed to subside, 
the clear solution siphoned off, and the precipitate repeat- 
edly washed by decantation ; the compound, however, 
tends to retain water and salts in considerable quantities. 
When dried on a tile it approximates to the composition : 

Ti0 3 + 3H 3 0.* 



PREPARATION OF VANADYL TRICHLORIDE. 

Extraction of Vanadium from Its Ores. 

For the extraction of vanadium from its ores advantage 
is taken of the volatility of vanadyl trichloride. The 
finely divided mineral is intimately mixed with about 
one quarter of its weight of lamp black and a little oil, and 
ignited to volatilize the arsenic and zinc. The calcined 
product is then slowly heated to 13 1° C. in a stream of dry 
chlorine, and the vanadyl trichloride collected in tubes im. 
mersed in a freezing mixture. When it is desired to 
determine the quantity of vanadium in an ore, the above 
method is employed, and the vanadyl trichloride is col- 
lected in a series of bulbs containing distilled water ; the 
vanadic acid is then reduced with zinc, and estimated volu- 
metrically with the aid of potassium permanganate.! 



* A. Classen, Ber. 21, 370. 

f By L. L'Hote Ann. Chim. Phys. [6], 22, 407-412. 



INORGANIC PREPARATIONS. 6j 



VANADYL CHLORIDE. 

Prepared from vanadianite (14.42% V 2 5 ) by mixing 
the powdered mineral with four times its weight of lamp 
black, making into a paste with oil and calcining. The 
calcined product is then heated in an oil bath in a current 
of dry chlorine, care being taken to prevent the tempera- 
ture exceeding 13 1° C. Pure vanadyl chloride begins to 
distill at98° C, and if the temperature is raised to 131 °C. 
the whole of the vanadium in the mineral is converted into 
this compound.* 



AMMONIUM BICARBONATE. 

(NH 4 )HC0 3 . 

Pour cone, aqua ammonia into a small flask and close 
it with a stopper attached to a short glass tube, through 
which carbonic acid is passed. The neutral ammonium car- 
bonate which precipitates at first, redissolves, and after the 
liquid has for a time been subjected to the carbonic acid, 
the acid salt separates. More bicarbonate may be obtained 
from the mother liquor by mixing it with alcohol. It is 
preserved in glass tubes which are filled with carbonic acid 
and sealed. 

Ammonium bicarbonate crystallizes in hard, glossy, 
rhombic prisms, very readily volatile. The aqueous solu- 
tion must not be rendered turbid by the addition of 
calcium chloride. 



By L. L'Hote, Compt. Rend. 101-1151, 



68 LABORATORY MANUAL OF 



AMMONIUM BROMIDE. 
NH 4 Br. 

AND 

POTASSIUM BROMIDE. 
KBr. 

From a dropping funnel with a finely drawn out stem 
75 c. c. of bromine are allowed to flow, slowly and with con- 
tinual shaking, into 220 c. c. of cone. (30%) ammonia con- 
tained in a flask cooled with ice-water, taking care that the 
liquid shall remain strongly ammoniacal at the end of the 
reaction. It is then boiled until the free ammonia has 
been driven out and evaporated to crystallization. The 
ammonium bromide is dried by gently heating in a porce- 
lain dish over an open fire. 196 grams ammonium bro- 
mide are dissolved in hot water, 200 grams potassium 
bicarbonate added, and the whole is heated to boiling ; 
when the ammonia has been driven out it is allowed 
to crystallize : 

4NH3+3Br=3NH 4 Br+N. 

If the solution should become acid, or the bromine 
flow in too rapidly, there might be a formation of nitrogen 
bromide which would cause an explosion. 

As a test a small sample of the salt is boiled in a re- 
tort with a large excess of iron-ammonia alum in aqueous 
solution, whereby any iodine which may be present will 
pass over in a free state ; remove the bromine from the 
residue by addition of potassium permanganate solution 
and test for chlorine. This separation of the halo- 



INORGANIC PREPARATIONS. 69 

genes depends on the fact that ferric salts will set free 
iodine from neutral solutions of the iodides : 

Fe 2 (S0 4 ) 3 + 2KI = 2FeS0 4 + K2SO4 + 21. 

while the bromides remain unchanged. 

On the other hand, these are also entirely decomposed 
if a small quantity of a strong oxydizing agent (perman- 
ganate) is present. The chlorides resist the simultaneous 
influence of these two agents. 



PREPARATION OF AMMONIUM PERSULPHATE. 

A porous clay cell (80 to 100 c. c. capacity), containing 
a saturated solution of ammonium sulphate in a mixture 
of 1 part by volume of sulphuric acid with 8 parts by 
volume of water is placed in a beaker and surrounded by 
a mixture of equal volumes of sulphuric acid and water. 
A lead cylinder, placed round the porous cell, serves as 
the carthode and a platinum spiral, having a surface of 0.5 
sq. cen., is suspended inside the porous cell to serve as the 
anode. The beaker is embedded in ice. The electrolysis 
is effected by a current of 2 to 3 amperes ; some 8 volts will 
be necessary when the internal resistance of the decom- 
posing cell is about 1 ohm. After 2 to 3 hours the contents 
of the porous cell are filtered through glasswool and the 
crystals of ammonium persulphate dried on a porous 
plate ; the filtrate is shaken with ammonium sulphate and 
once more electrolysed. 20 to 40 grains of the persulphate 
may thus be obtained in one operation, the yield being 
least at the outset, when the liquor is being saturated 



JO LABORATORY MANUAL OF 

with the persulphate. The sulphuric acid in the outer 
cell eventually becomes alkaline from the transit of the 
ammonium, and pari passu the ammonium sulphate 
in the inner cell becomes strongly acid ; from time to 
time the former liquid must be renewed and the latter 
nearly neutralized with ammonia. To recover the per- 
sulphate left in the liquor when the preparation has been 
completed a concentrated solution of potassium carbonate 
or acetate is added ; potassium persulphate will thus be 
precipitated, as ioo parts of water only dissolve 2 parts of 
this salt, whereas they dissolve 65 parts of the ammonium 
salt.* 

Ammonium persulphate thus prepared contains some 
3 to 5 per cent, of impurities, consisting chiefly of ammo- 
nium sulphate, but partly of ammonium alum, derived 
from the clay of the porous cell. It may be recrystallized 
from water. 



AMMONIUM DICHROMATE. 
(NH 4 ) 3 Cr 3 7 . 

Chrome iron ore is heated with sodium or potassium 
salts ; the resulting monochromate is dissolved in water, 
treated with 2 equivalents of acids, and then neu- 
trallized with ammonia or ammonium carbonate. The 
solution containing a dichromate and sulphate, chloride, 
or nitrate, as the case may be, is concentrated ; the latter 
salts as they crystallize are removed, and finally on cool- 



By K. Elbs, J. pr. Chem. [2] 48, 185-189. 



INORGANIC PREPARATIONS. J\ 

ing ammonium dichromate crystallizes out. The potas- 
sium or sodium salts are used again for heating with fresh 
chrome iron ore.* 



AMMONIUM NITRATE. 
NH4NO3. 

The mixture of nitrogen oxides evolved during the 
action of arsenious anhydride or nitric acid is passed over 
coarsely powdered ammonium carbonate kept cool by 
ice. The half liquid mass is treated with alcohol, the un- 
changed carbonate filtered off, and the ammonium nitrate 
precipitated by means of ether. The nitrate so obtained 
is of 90 to 94 per cent, purity, and may be purified by 
resolution in 96 per cent, alcohol and reprecipitation 
with ether. Pure ammonium nitrate forms almost color- 
less needles, which are deliquescent and dissolve in water 
with development of heat. It is easily but slowly soluble 
in alcohol, and is precipitated from this solution by ether, 
chloroform or ethylic acetate. Concentrated solutions ap- 
pear to decompose with explosive violence at 6o° to yo° C, 
like the solid salt, and in acid solutions, such decomposi- 
tion sometimes occurs at ordinary temperatures. The dry 
salt may be safely kept in an atmosphere of hydrogen and 
in presence of pieces of ammonium carbonate and of lime. 
It is best kept and transported under absolutely dry and 
alcohol free ether, t 



* T. J. Hood, Chem. Zeit. 11, 55. 

f S. P. L. Sorensen, Zeit. anorg. Chem., 7, 33. 



72 LABORATORY MANUAL OF 



AMMONIUM DI HYDROGEN PHOSPHITE. 
NH4H5POJJ. 

A solution of phosphorous acid mixed with ammonia 
until neutral to methyl orange, and then concentrated 
until the weight of the liquid is one-fourth or one-fifth 
more than the calculated weight of the salt, yields large 
deliquescent crystals, which can be dried over sulphuric 
acid or at ioo° C. Similar crystals are obtained if the 
liquid is concentrated in vacuo at ordinary temperature. 
The crystals have the composition NH 4 H 2 P0 3 , and seem 
to be monoclinic prisms; they melt at 123° C. and are 
very soluble in water. At 145 C. they lose half their 
ammonia without evolution of hydrogen phosphide and 
yield a gummy mass which seems to contain crystals. 
At a higher temperature ammonia and hydrogen phos- 
phide are given off and phosphoric acid is formed.* 



AMMONIO ZINC CHLORIDES. 

If a stream of ammonia is passed into a hot concen- 
trated solution of zinc chloride until the precipitate first 
formed is redissolved, and the whole is then allowed to 
cool, nacreous scales of the composition ZnCl 2 , 4NH3+ H 2 
crystallize out. On concentration the mother liquor yields 
crystals of the formula ZnCl 2 , 2NH3 ; this compound 
separates in colorless rhombic crystals, which do not 



* L. Amat. Compt. Rend., 105, 809. 



INORGANIC PREPARATIONS. 73 

change on exposure to air. It is insoluble in water, but 
when boiled with it decomposes with evolution of am- 
monia. It is easily soluble in solutions of ammonia or 
ammonium chloride. The same compound is also formed 
when ammonia is added to a cold dilute solution of zinc 
chloride until the precipitate first formed is redissolved, or 
when freshly precipitated zinc hydroxide is dissolved in 
a concentrated solution of ammonium chloride. The same 
compounds, in well formed crystals, has also been found 
in Leclanche cells. The constitution is probably expressed 
by the formula NH 3 Cl.Zn.NH 3 Cl.* 



CUPROUS CHLORIDE. 
CuoCls. 

Cuprous Chloride can be conveniently prepared by 
heating a mixture of copper sulphate (4 grams) and so- 
dium hypophosphite (2 grams) in about 50 c. c. of 
water to which 30 drops of fuming hydrochloric acid are 
added. 

The cuprous chloride is deposited and can be purified 
in the ordinary way. The change can be explained thus : 
Copper hypophosphite is at first formed, and this is con- 
verted by the hydrochloric acid into cuprous chloride and 
phosphoric acid. The equation is as follows : 2CuCl 2 + 
H 3 P0 2 + H 2 = H3PO3 + 2HC1 + Cu 2 Cl 2 . 

Another method of preparation is to pour 100 c. c. 
hot water over 42 grams copper chloride (cryst.) and 
32 grams metallic copper (granulated or turnings) ; add 



H. Thomas, Ber., 20, 743. 



74 LABORATORY MANUAL OP 

200 c. c. crude hydrochloric acid (sp. gr. 1.175), and boil 
gently in a flask closed by a small funnel ; finally add a 
little fuming hydrochloric acid and boil until the solution 
becomes colorless. This operation lasts one to two hours, 
but can be hastened considerably if the copper powder in 
cakes obtained in preparing blue vitriol is added to the 
solution. The colorless solution is poured off from the 
surplus copper into a cylinder filled with cold distilled 
water, the cheesy precipitated protochloride is allowed to 
settle and decanted immediately, quickly filtered, washed 
with ether and alcohol, and dried in vacuum over sul- 
phuric acid. 

CuCl 2 + Cu = Cu 2 Cl 3 . # 
Cuprous chloride forms in heavy white masses, insolu- 
ble in water, and oxydizes easily in the air and, with 
chlorine water or aqua regia (nitromuriatic acid), dissolve 
readily as copper chloride. By heating in small tubes 
the protochloride melts without decomposition. 



CUPROUS CYANIDE. 

(Cu 2 CN) 2 . 

50 grams crystallized blue vitriol are dissolved in 300 
c. c. hot water, and to this hot solution in a flask, add, 
by means of a dropping funnel, a solution of 26 grams 
potassium cyanide in 50 c. c. water. The escaping cy- 
anogen gas is passed through a glass tube bent upward, 
tapering to a point and lighted at the end of the tube as 
soon as the apparatus is filled with it. The gas is very 



By A Cavazzi, Gazzetta 16, 167-168). 



INORGANIC PREPARATIONS. 75 

poisonous and burning is a ready way of getting rid of it. 
The white cheesy sediment is separated by decanting from 
the faintly bluish-colored solution, washed with water and 
dried on an earthen plate. 

CuS0 4 4- 2KCN = Cu(CN) 3 -f K 3 S0 4 . 
2Cu(CNj 3 = Cu 3 (CN) 3 + CN 2 . 
Cuprous chloride is a tolerably stable white powder, 
similar on the whole to the copper protochloride. Decom- 
poses by heating, with a cyanogen odor. 



COPPER AMMONIUM SULPHATE. 
(NH 3 ) 4 CuS0 4 . 

COPPER POTASSIUM SULPHATE. 
CuK 3 (SO) 2 + 6H 2 0. 
Ammonium double-salt. — 30 grams blue vitriol are 
dissolved in 100 c. c. ammonia-solution of 0,962 sp. gr. 
150 c. c. alcohol are then placed into a high, narrow cy- 
linder, and by means of a long-stemmed dropping funnel 
20 c. c. water are carefully poured into the alcohol ; then 
the copper solution is added in a very fine stream, so that 
it will gather at the bottom of the cylinder, and is 
separated from the alcohol by the water. Upon standing 
from 1 to 4 weeks it forms large dark blue crystals. 

Potassium double-salt. — 100 grams blue vitriol in a 
saturated solution at 70 C. are mixed with a solution of 
69,8 grams potassium sulphate and 7 c. c. cone, sulphuric 
acid. On cooling the whitish-blue crystals of the double- 
salt separate. 

Determine the copper value of the salts : Of the am- 



y6 LABORATORY MANUAL OF 

monia double-salt by simply annealing and weighing the 
remaining copper oxide; of the potassium double-salt by 
precipitating with a piece of cadmium or zinc in a weighed 
platinum dish from the diluted solution made faintly acid 
with hydrochloric acid. When a sample of the discolored 
solution no longer reacts with sulphureted hydrogen water, 
rinse with a little hydrochloric acid, then with hot water, 
and lastly with alcohol; dry at ioo° C. and weigh. 



CUPRIC SULPHATE. 
CuS0 4 ,5H 2 0. 

This reagent may be obtained in a state of great purity 
from the residue remaining in the flask in the process of 
preparing hydrogen sodium sulphite by treating with 
water, applying heat, filtering, adding a few drops of nitric 
acid, boiling for some time, allowing to crystalize, rnd 
purifying the salt by recrystallization. 

After precipitation by hydrogen sulphide, ammonia 
and ammonium sulphide must leave the filtrate unaltered. 



CUPRO US OXIDE. 
Cu 2 0. 
A fairly concentrated solution of copper sulphate along 
with excess of sodium chloride is thoroughly reduced by 
treatment with gaseous sulphurous anhydride ; the excess 
of the latter is then expelled by heating, and solid sodium 
carbonate is added to the hot solution ; bright red cuprous 
oxide is precipitated, and is readily washed by decantation.* 



E. J. Russell, Chem. News, 68, 308. 



INORGANIC PREPARATIONS. J? 



CUPROUS AMMONIUM IODIDE. 
4NH 3 Cu 3 I 4 . 

IOO grams of an ammoniacal solution of cupric oxide 
containing 7 to 8 per cent, is mixed with an equal weight 
of a 10 per cent solution of iodine in alcohol. A brown 
precipitate of nitrogen iodide is formed, but this readily 
disappears on warming, and if the liquid is heated for about 
an hour on the water bath it becomes green and deposits 
brilliant green needles, which must be dried as quickly as 
possible. They have the composition 4NH 3 ,Cu 3 I 4 or 
4NH 3 Cu 2 I 2 ,CuI 2 and alter rapidly when exposed to air, 
losing ammonia and iodine, and eventually changing to 
cuprous iodide. The crystals are insoluble in water, but 
are decomposed by prolonged boiling. They are only de- 
composed by potash after prolonged boiling, but they 
dissolve readily in ammonia, and the solution yields cu- 
prammonium iodide when evaporated. If the green solu- 
tion obtained as above is boiled with metallic copper until 
it becomes colorless and is then allowed to cool, it deposits 
cuprosoammonium iodide in brilliant white needles 5 to 6 
mm. long. If the mixture of ammoniacal copper solution 
and alcoholic iodine is allowed to stand with exposure to 
air at the ordinary temperature, the nitrogen iodide slowly 
dissolves, and after some hours the liquid deposits cupram- 
monium iodide in octahedral crystals. If the ammoniacal 
solution is boiled with iodine for several hours without ad- 
dition of alcohol, and is then cooled, it deposits cupram- 
monium iodide in tetrahedral crystals. 



78 LABORATORY MANUAL OF 



CUPROAMMONIUM TETRA IODIDE. 
4NH 3 CuI 2 ,I 3 . 

Is obtained in brilliant black crystals, green by trans- 
mitted light, by boiling ioo c. c. of the ammoniacal copper 
solution with 20 grams of iodine, and allowing the liquid 
to cool. If a further quantity of 20 grams of iodine is dis- 
solved in the mother liquid from these crystals, the liquid on 
cooling deposits cuproammonium hexiodide 4NH 3 ,CuI 2 I 4 , 
in rectangular tablets, which are brown by transmitted 
light. This compound is usually obtained by mixing a 
warm solution of cuproammonium nitrate with a solution 
of iodine in potassium iodide. 



CUPROUS PHOSPHIDE. 
Cu 2 P 2 . 
When red phosphorous is immersed in an ammoniacal 
solution of copper sulphate, it becomes coated, as is well 
known, with a greyish deposit, which is a mixture of 
cuprous phosphide and metallic copper ; the same occurs 
with an ammoniacal solution of copper phosphate, but the 
transformation is never complete, even at ioo Q C. If, 
however, red phosphorous is heated with a large excess of 
copper phosphite and water in a sealed tube for four hours 
at 130 C, its entire conversion is effected. The product 
is washed quickly with aqueous ammonia and water in 
succession, and dried in a vacuum. If the temperature hac 
not exceeded that specified, it is not contaminated with 
metallic copper.* 

* By A. Granger, Compt. rend., 117, 231-232. 



INORGANIC PREPARATIONS. 79 

Cuprous phosphide, Cu 2 ,P 3 , is a grey powder resembling- 
plumbago in appearance. It is attacked by chlorine and 
bromine in the cold, and is readily dissolved by dilute 
acetic acid ; a mixture of it with potassium nitrate or 
chlorate detonates violently when struck. When heated 
in contact with air, it is oxydized to copper phosphate. It 
is decomposed by heat into products identical with those 
yielded by cupric phosphide. It is slightly soluble in 
hydrochloric acid, yielding a solution from which cuprous 
oxide is precipitated by potash, and which, when super- 
saturated with ammonia, precipitates metallic silver from 
a n ammoniacal solution of silver nitrate. 



PURE SILVER. 

Ag. 

a. Crystallized Silver. — Any weighed quantity of 
technical silver (coin or broken plate) is dissolved in 
nitric acid, filtered and dried. The dried mass is 
fused until it begins to turn black, dissolved in water, 
filtered and diluted to such a degree that the solu- 
tion contains 2 per cent, silver. It is now made 
strongly ammoniacal in the cold and sodium bisulphite 
solution added until a sample of the blue solution is de- 
colorized on boiling. The greater part of the silver 
separates in crystals as the solution cools, the remainder 
by warming at 6o Q to 70 s C. The silver is washed with 
water, then digested several times with concentrated am- 
monia, again washed with water, dried on the waterbath 
and weighed. 

b. Molecular Silver from Residues. — Silver residues 
together with zinc sticks are boiled with addition of hy- 



80 LABORATORY MANUAL OF 

drochloric acid. The reduced silver, freed mechanically 
from the undissolved zinc, is washed well by decantation, 
then dissolved in nitric acid and precipitated with hydro- 
chloric acid. The decanted and washed silver chloride is 
placed, while still moist, in soda lye, kept boiling in a porce- 
lain dish and adding at intervals a few c. c. of cone, grape 
sugar solution, until a filtered and washed sample of the 
gray silver powder dissolves completely in nitric acid. 
Wash, dry and weigh as described in a. 

The black color appearing in fusing the impure nitrate 
arises from the decomposition of the copper nitrate ; 
to avoid any loss of silver it is not heated until all the 
copper salt has been converted into oxide ; but the separa- 
tion of silver from the copper is so managed that the silver 
from the ammoniacal solution is precipitated in metallic 
form by sulphurous acid, while the copper, under these 
circumstances, is reduced to protoxide, which remains dis- 
solved in the ammoniacal solution. 

Dissolve a sample of the silver in nitric acid free from 
chloride, and note any sediment (gold, silver, chloride, tin 
dioxide) ; precipitate the solution with hydrochloric acid 
and test the filtrate for heavy metals. 



PREPARATION OF PURE COLLOIDAL SILVER. 

Solutions of ferrous sulphate (150 grams of the salt in 
500 c. c. of the solution; and of sodium citrate (280 grams 
of the salt in 700 c. c. of the solution) are mixed and 
poured into a 10 per cent, solution of silver nitrate (500 



INORGANIC PREPARATIONS. 8 I 

c. c). Day-light need not be excluded, but it is ad- 
visable to divide the mixture into five equal portions, as 
small quantities can be dealt with more easily than large. 
At the end of half an hour the supernatant liquid is re- 
moved from the precipitated colloidal silver with a pipette, 
and the silver is thrown on to a filter (Schleicher and 
Schiill's No. 590 paper), filtered under diminished pressure, 
and dissolved on the filter in the minimum quantity of 
water ; solutions may thus be obtained containing 20 
grams of silver per litre. To this solution absolute alcohol 
is added ivith agitation until coagulation is perceptible, 
and, after remaining for several days, the colloid is fil- 
tered under a diminished pressure of 10 to 20 mm. on a 
Pasteur filter-tube, when it forms a beautiful iridescent 
incrustation. Colloidal silver in this state of purity is 
soluble in alcohol, and cannot therefore be washed with 
this liquid to remove the last traces of crystalloids. By 
this method a product containing only .03 to .05 percent, of 
iron is obtained.* 



SILVER POTASSIUM CARBONATE. 
AgKCOg. 

150 grams of potassium carbonate are dissolved in 150 
c. c. of water, cooled and agitated with 1 5 grams of potas- 
sium hydrogen carbonate. When the liquid is saturated 
with the latter salt at ordinary temperature, it is filtered 
and mixed with a solution of one gram of silver nitrate in 
25 c. c. of water. In order to obtain large crystals, the liquid 
containing the precipitate is heated with continual agita- 

* By E. A Schneider, Ber. 25, 1281-1284. 
6 



82 LABORATORY MANUAL OF 

tion. The precipitate dissolves, and when the liquid is 
cooled it deposits long, transparent crystals with a brilliant 
lustre: sp. gr. 3.769. They do not blacken when exposed 
to light except in the presence of organic matter, and when 
treated with water the silver carbonate which remains re- 
tains the form of the original crystals. When heated the 
compound loses carbonic anhydride, and at a higher tem- 
perature the silver oxide which is formed gives off oxygen. 
The crystals are microscopic, rectangular lamellae with 
a terminal angle closely approaching 90 . The refraction 
is almost identical with that of apatite.* 



PURE GOLD. 

Au. 
Technical gold (broken pieces of jewelry, a coin or crude 
washgold) is broken into pieces as small as possible, weighed, 
placed in a small flask and concentrated hydrochloric acid 
poured over it. The flask is heated in a sand-bath, and 
from time to time cone, nitric acid dropped into it. After 
all is dissolved evaporate in a porcelain dish on the water- 
bath, carefully avoiding all dust, until the remaining dark- 
red solution solidifies on cooling. Then dissolve in plenty 
of water, filter from the separated silver chloride and pre- 
cipitate the filtrate hot with ferrous chloride solution in 
excess. The separated gold in powder is decanted, boiled 
several times with diluted hydrochloric acid, gathered on 
an ashless filter, fused in a porcelain crucible and weighed. 
In case larger quantities of gold are refined, a little platinum 



* A de Schulten, Compt. Rend. 105, 811. 



INORGANIC PREPARATIONS. 83 

and palladium (even thallium) can be separated from the 
filtrate with iron or zinc. 

The gold obtained in form of a reddish powder should 
not impart a trace of yellowish color (iron) to boiling hy- 
drochloric acid. If a weighed quantity is once more 
subjected to the refining process described above the 
weight should remain constant. 



AURIC CHLORIDE, OR GOLD TRICHLORIDE. 

AuCl 3 . 
Take fine shreds of gold, which may be alloyed with 
silver or copper, treat them in a flask with nitrohydrochloric 
acid in excess, and apply a gentle heat until no more of 
the metal dissolves, then dilute the solution with 10 parts 
of water. If the gold was alloyed with copper — which is 
known by the brownish-red precipitate produced by po- 
tassium ferrocyanide in a portion of the solution diluted 
with water — mix it with solution of ferrous sulphate in 
excess. This will reduce the auric chloride to metallic 
gold, which will separate in the form of a fine brownish- 
black powder ; wash the powder in a small flask, and dis- 
solve it in nitrohydrochloric acid ; evaporate the solution 
on the waterbath, and dissolve the residue in 30 parts of 
water. If the gold was alloyed with silver, the latter 
metal remains as chloride, upon treating the alloy with 
nitrohydrochloric acid. In that case evaporate the solu- 
tion at once, and dissolve the residue in water for use. 



84 LABORATORY MANUAL OF 



AUROSO-AURIC CHLORIDE. 

Au 2 Cl 4 . 
By leading a stream of dry chlorine for 30 minutes 
over gold, precipitated from a solution of gold chloride by 
sulphurous acid, 50 to 70 grams of gold may be converted 
into a homogeneous mass corresponding with the formula 
AugCl^. The reaction is started by gentle heating, but the 
necessary temperature is then maintained by the heat 
evolved in the reaction, provided that cooling is prevented 
by surrounding the tube with cotton or glass wool.* 



ANHYDROUS MAGNESIUM CHLORIDE. 

MgCL, 
500 grams crytallized magnesium chloride and 500 
grams sal ammoniac are dissolved in a very small quantity 
of water, filtered in a porcelain dish and dried in a silver 
dish. The solid mass is broken while hot and dried in 
small portions on porcelain or, better, on platinum dishes 
(the mixture corrodes base metals, silver also, at a higher 
temperature). The operation occupies some time and is 
to be carried out with great care, as even very small 
quantities of water frustrate the success of the experi- 
ment. Dry in portions on several gas stoves and regulate 
the heat so that an escape of ammonium chloride vapor does 
not take place. Powder the portions from time to time in 
a hot mortar, continue drying until the product, on heat- 



J. Thomsen, J. pr. Chem. [2] 37, 105. 



INORGANIC PREPARATIONS. 85 

ing, no longer cakes and only consider the operation 
completed when a sample heated in a test tube shows no 
moisture ; after driving off the ammonium chloride there 
remains a clear solution, forming radiant crystals upon 
cooling. Then pour the powder* while still hot in a 
spacious platinum crucible, close with a well-fitting cover 
and place into the Roessler furnace which has previously 
been heated. After the ammonium chloride is driven out, 
again fill the crucible t with the loose powder, and con- 
tinue heating until the entire mass is fused. The solidified 
magnesium chloride, which is easily removed from the 
crucible, should be placed in a well-stoppered bottle while 
still warm. 

Crystallized magnesium chloride can be rendered an- 
hydrous and the formation of a basic salt prevented by 
heating it in a current of hydrogen chloride.^: 

Crystallized magnesium chloride on heating loses the 
largest quantity of its chlorine in the form of hydrochloric 
acid; on the other hand, the double-salt (NH 4 ) 2 MgCl 4 
can, by heating carefully, be volatilized without decompo- 
sition. On igniting this double-salt anhydrous magnesium 
chloride remains. 

(NH 4 ) 2 MgCl 4 = MgCl 2 + 2NH 4 C1. 

Magnesium chloride crystallizes in large radiant g^ssy 
crystals, not unlike fused sodium acetate, which melt readily 
on heating and volatilize at red-heat. The vapors decom- 



* If the dried substance is to be preserved, this must be done in well- 
stoppered vessels. Before using the mass it should be dried for a short time 
on the gas stove. 

f When in a red-hot condition the crucible must not be opened on 
account of the volatility of the magnesium chloride. 
\ W. Hempel, Ber. 21, 897. 



$6 LABORATORY MANUAL OF 

pose aqueous vapor instantly, forming hydrogen chloride. 
The very hydroscopic salt should form a clear solution in 
warm water. 



CRYSTALLIZED NORMAL MAGNESIUM CAR- 
BONATE. 
MgC0 3 + 3H 2 0. 

If freshly precipitated magnesium carbonate, made by 
mixing equivalent amounts of magnesium sulphate and so- 
dium carbonate,is shaken with a solution of potassium hydro- 
gen carbonate at the ordinary temperature, much of the mag- 
nesium carbonate dissolves, crystallizes out of the filtered 
solution after a time ; the separation is ended in 24 hours. 
The same occurs if sodium hydrogen carbonate is used ; it 
dissolves relatively more of the magnesium carbonate, but 
the crystals obtained are smaller. Solutions containing 
respectively 67.5 grams of potassium and 12.96 grams of 
sodium hydrogen carbonate per liter dissolved, respectively, 
18.73 and 9.95 grams of magnesium carbonate. The crys- 
tals have the composition 4MgCo 3 + 15H 3 ; after four 
weeks in dry air, or 15 hours in a vacuum dessicator 
over sulphuric acid, they have the composition 2MgC0 3 4- 
6H 3 0; after heating at 170 C. the composition MgC0 3 + 
1 / s — VeH^O. The reaction is that a double sesquicarbonate 
of magnesium and the alkali metal is formed, and that this 
afterwards decomposes, magnesium carbonate being pre- 
cipitated, and carbonic anhydride liberated, which latter 
regenerates the alkali bicarbonate with the alkali sesqui- 
carbonate now present. 

Alkali bicarbonates do not dissolve calcium carbonate 



INORGANIC PREPARATIONS. 87 

or ferric hydroxide, and upon this fact a technical process 
for the preparation of pure magnesium carbonate from 
dolomite, magnesite, bitterspar and from kanite or caen- 
allite liquors has been based. The mineral is powdered, 
dissolved in commercial hydrychloric acid and the iron 
oxydized by warming gently with a little nitric acid. The 
solution is then precipitated with sodium carbonate in slight 
excess, the filtered precipitate shaken with a sufficiently 
strong solution of alkali bicarbonate, and the solution fil- 
tered after a lapse of 20 minutes and set aside to crystal- 
lize. The mother liquor can be used repeatedly for the 
extraction.* 



MAGNESIUM BASIC CARBONATE. 
Mg(OH) 2 ,MgC0 3 . 
Prepare a strong solution of magnesium sulphate in 
water, kieserite serves very well ; to the cold filtered solu- 
tion add sodium carbonate solution in slight excess, mix 
well in the cold, filter and wash slightly ; the filtrate may 
be used to prepare glauber-salt ; transfer the precipitate 
of magnesium carbonate to a suitable vessel, add water and 
boil for 1 5 minutes ; filter and wash on a filtering plate, 
suck as dry as possible, remove from filter and dry at 
ioo° C. 

POROUS CALCIUM CHLORIDE. 

CaClg. 
One litre of the solution remaining from the evolution 
of carbonic acid from marble and hydrochloric acid (crude) 



K. Kippenberger, Zeit. anor. Chem. 6, 177. 



88 LABORATORY MANUAL OF 

and which no longer reacts with marble is warmed and 
then precipitated with milk of lime, made from 35 grams 
caustic lime, in an iron pot of 2 litres capacity and filtered.* 
After the strongly alkaline solution has been boiled, mix 
the filtrate with hydrochloric acid to a strong acid reaction 
and evaporate it on the gas stove, with further addition of 
acid, in- a porcelain dish of j£ litre capacity As soon as 
a coating of salt begins to form the heat is reduced, a little 
fuming hydrochloric acid is added, and the whole left stand- 
ing quietly without stirring ; the mass becomes entirely dry 
in the course of from four to five hours. Now carefully re- 
move the calcium chloride from the dish with a knife, 
break the large pieces while still hot in a warm mortar, 
screen the pieces as quickly as possible in sieves from 1 to 5 
mm mesh, and fill immediately into well-stopperd speci- 
men bottles. 

The caustic lime precipitates from the marble solution 
magnesia, as well as the oxides of iron and manganese 
(Very often in standing, basic calcium chloride 3CaO, 
CaClg + 15H 3 separates from the filtrate in long prisms). 
In evaporating to dryness the solution must be acidified 
with hydrochloric acid and the heating must be a gradual 
one, otherwise the calcium chloride will lose HC1. and 
take on a strong alkaline reaction. 

Porous calcium chloride is a pure white, porous, very 
hydroscopic mass, which dissolves clearly in water, and in 
alcohol the water solution should show a reaction which is 
slightly alkaline. 



* In place of this you can also proceed from the residue of ammonia 
production, consisting- of a mixture of calcium chloride and surplus lime. 
Boil the same with water until the last traces of ammonia have passed away, 
then filter and continue as stated above. 



INORGANIC PREPARATIONS. 89 



CALCIUM CHLORIDE. 

CaCl2, crystat/izca 7 -\-6H 2 0. 

Dilute I part of crude hydrochloric acid with 6 parts ot 
water, and add thereto marble or chalk until the last por- 
tion added remains undissolved ; add now some slacked 
lime, then hydrogen sulphide, until a filtered portion of the 
mixture is no longer altered by ammonium sulphide. 
Then let the mixture stand covered for 12 hours at a 
gentle heat, filter, exactly neutralize the filtrate, concen- 
trate by evaporation and crystallize. 

Solution of pure calcium chloride must be perfectly 
neutral, and neither be colored or precipitated by ammo- 
nium sulphide ; nor ought it to evolve ammonia when 
mixed with potassa or lime. 



Calcium carbonate. 

CaCo 3 . 
Solution of pure calcium chloride is heated to boiling 
and precipitated by a slight excess of solution of ammo- 
nium carbonate with addition of some ammonia. The 
precipitate is washed five or six times with hot water by 
decantation, then is brought upon a filter and further edul- 
corated until the washings give no turbidity with silver 
nitrate. The contents of the filter are then dried and 
bottled. 

Calcium carbonate for use as a flux must be free from 
salts of the fixed alkalies. When washed with hot water 
the washing must yield no residue when evaporated to 
dryness. 



90 LABORATORY MANUAL OF 

CRYSTALLINE MONOCALCIUM PHOSPHATE. 
CaH 4 (P0 4 ),. 
Neither the crystalline nor the honey-like commercial 
variety of monocalcium phosphate corresponds with the for- 
mula CaH 4 (P0 4 ) 2 , owing to the free sulphuric acid in 
the crude liquor acting on the phosphate during evapora- 
tion. By leaving tricalcium phosphate in contact with a 
solution of the honey-like commercial variety for some 
time, a solution is obtained which, on gentle evaporation, 
yields crystals of pure monocalcium phosphate.* 



CALCIUM CHROMATE. 
CaCr 3 4 . 
The process is based on the fact that when chromium 
oxide (Cr 3 3 ) is heated with a mixture of calcium chloride 
and oxide, a chromite is formed (CaCr 2 4 ) which absorbs 
oxygen from the air and yields calcium chromate. The 
finely powdered mineral is mixed with paste composed of 
lime, calcium carbonate and a concentrated solution of 
calcium chloride, in such proportion that the lime and 
the calcium carbonate are slightly in excess, of the amount 
necessary to combine with the chromium oxide present, 
while the calcium chloride is about one-third of the total 
lime used. The mixture, on exposure to air, hardens and 
is moulded into bricks, which are dried and subsequently 
roasted at a temperature sufficient to convert the calcium 
carbonate into lime. The bricks are exposed to the action 
of air for about one month, then lixiviated with hot water 
to remove the calcium chloride, and the residue containing 



* G. Pointet, Bull. Soc. Chim. [3] 5, 254. 



INORGANIC PREPARATIONS. 9 1 

the calcium chromate is treated with alkali carbonate or 
sulphuric acid in the usual way, according as an alkali 
chromate or chromic acid is required.* 



ZINC FREE FROM ARSENIC. 

Zn. 
One kilo commercial zinc is melted in a hessian cru- 
cible. Into the red-hot metal plunge pieces of anhydrous 
magnesium chloride, forcing them to the bottom of the 
crucible, and allow them to remain there until dissolved. 
To retain the specifically light chloride below the fused 
metal an iron wire is employed, the lower part of which 
is twisted into a close spiral. Fasten in the small bell so 
constructed, the magnesium chloride by means of a little 
flower-wire, and press the wire into the metal. After 
adding 1 5 grams of the chloride allow the crucible to cool 
sufficiently to prevent the metal from igniting upon open- 
ing it, and (the metal should be still liquid) pour it in 
the finest possible stream into a pail of water. The gran- 
ules upon removal from the water are drained and dried 

by heat 

3MgCl 2 + 2As = 3Mg + 2AsCl 3 . 
The arsenic chloride and undecomposed magnesium chlo- 
ride pass off in thick clouds. 

The zinc so obtained contains magnesium and, so dif- 
ferently from c. p. zinc, dissolves very readily in diluted 
acids. To test it for arsenic, pour over it, in a test tube, 
dilute (1.1) hydrochloric acid and cover the tube with a 
small filter, the tip of which is moistened with a drop of 



* J. Massignon and E. Vatsl, Bull. Soc. Chim. [3] 5, 371. 



92 LABORATORY MANUAL OF 

cone, silver solution (i.i). Yellow silver arsenite Ag 3 As0 3 
forms after a time, which turns black and decomposes in 
water. * 



ZINC EISEN. 
From one ro two pounds of zinc are melted in a clay 
crucible, 3 to 3.5 ozs. of anhydrous sodium ferrous chloride 
are thrown in, and the crucible is immediately covered ; 
violent reaction ensues, and the alloy is produced ; it is 
very brittle, has a full metallic lustre, and is easily pul- 
verized. f 



STRONTIUM HYDROXIDE. 
Sr(OH) 2 + 8H 3 0. 
A well mixed mass of 150 grams finely powdered 
celestine and 50 grams wood charcoal is pressed into a 
hessian crucible and covered with a layer of powdered 
coal. Close the crucible with an accurately fitting iron 
cover, provided with a rim, and heat at white heat for an 
hour in the Roessler gas furnace. The cool product should 
dissolve in dilute hydrochloric acid with vigorous evolution 
of sulphureted hydrogen, leaving only a slight coaly 
residue ; test a portion in this manner : Suspend the mass 
in a porcelain dish in a litre of hot water, and add to the 
solution scales of copper (100 to 150 grams which have been 
moistened with a little HNO3 and then annealed), until a 
filtered sample treated with lead acetate no longer pro- 



* L. L'Hote, Compound gS, 1491. 

f H. N. Warren, Chem. News, 55, 100. 



INORGANIC PREPARATIONS. 93 

duces a brownish-black precipitate. Then filter hot into a 
beaker, boil the residue with 100 c. c. water, cover the 
entire filtrate, and allow it to crystallize. After the lapse 
of 24 hours the liquid is poured off from the crystals, 
which are very quickly dried on an earthen plate and 
placed in a closed and paraffined vessel. The solution is 
rapidly evaporated to 300 c. c in an iron dish, to obtain a 
second crop of crystals. 

The strontium sulphate, by ignition with charcoal and 
exclusion of air, is transformed into strontium sulphide, 
which by the action of copper oxide is converted into stron- 
tium hydroxide: SrSo 4 +- 4C = SrS + 4CO ; SrS + CuO + 
H^O = Sr(OH 2 ) + CuS. 

Strontium hydroxide crystallizes in perfectly clear, 
easily efflorescent square tablets or needles of strong 
alkaline taste, dissolving readily and without residue in 
hot water. It melts easily on warming, and on further 
heating solidifies again to a white mass with loss of its eight 
molecules of water of crystallization; at higher tempera- 
tures it melts once more, and finally passes into strontium 
oxide. An acetic acid solution should not be precipitated 
by potassium dichromate (Barium), but should, on the 
other hand, be precipitated so completely by HgSO^ that 
ammonium oxalate does not form a precipitate in the 
filtrate (absence of lime). 



PREPARATION OF PURE STRONTIUM SALTS. 

The following process is given for obtaining a pure 

strontium salt from a barytostrontianite containing iron, 

aluminium, magnesium, calcium and barium as impurities: 



94 LABORATORY MANUAL OF 

The mineral or the sulphide resulting from the reduction 
of the sulphate is dissolved in such a quantity of hydro- 
chloric acid (20 per cent.) as to leave a little undissolved. 
The aluminum and iron are precipitated by ammonia, fil- 
tered off, and excess of sulphuric acid added. The pre- 
cipitate is washed first with dilute sulphuric acid (1 to 2 per 
cent.) and finally with water; it is thus freed from magne- 
sium and calcium. It is now digested in the cold for 
some days with ammonium or potassium carbonate solu- 
tion (10 per cent.), washed well, the residue treated with 
dilute hydrochloric acid, and the solution decanted ; 
after remaining for 24 hours this is filtered, and 200 grams 
of hydrochloric acid (sp. gr. 1. 1 7) per litre are added 
to it, together with 2 or 3 grams of precipitated strontium 
sulphate, which may contain barium. After some hours 
the solution is filtered, evaporated to dryness, dissolved in 
water, filtered and crystallized. The spectrum given by 
the salt thus obtained shows strontium to be the only metal 
present* 

CADMIUM CARBONATE. 
CdC0 3 . 
. IOO grams of cut or granulated commercial cadmium 
are placed in a flask with 400 c. c. cold nitric acid of 1.20 
sp. gr. Run the nitrogen dioxide evolved into the drain; 
after the action has completely ceased, pour the liquid 
from the undissolved residue into a porcelain dish of 6 
litres capacity ; dilute with 4 litres hot water and add a 
little powdered commercial ammonium carbonate, until a 



By Barthe and Falieres, Bull. soc. Chin. [3], 7, 104-108. 



INORGANIC PREPARATIONS. 95 

permanent precipitate is formed ; filter and precipitate the 
cadmium in the filtrate with about 150 grams ammonium 
carbonate ; decant several times with hot water in tall glass 
cylinders, and preserve the carbonate as paste, or else dry 
on the water-bath. 

3Cd + 8HNO3 =3Cd(N0 8 ) 2 + 2NO -f 4H 2 0. 

The foreign metals, with the exception of zinc and iron, do 
not remain in solution, but are again precipitated in me- 
tallic form by the surplus cadmium. The iron precipitates 
with the first portion of cadmium carbonate : 

3CdC0 3 i- Fe 2 (N0 3 ) 6 + 3H 2 = 3Cd(N0 3 ) 2 + Fe 2 (OH) 6 + 

SCO* 

The zinc is retained in solution by the surplus ammonium 
salt. 

The pure white salt passing into brown cadmium oxide 
on igniting, and easily dissolving in diluted acids with effer- 
vescence, is to be tested particularly for antimony, bismuth, 
copper, lead, iron and zinc according to the usual method 
of analysis. 



BARIUM OXIDE. 
BaO. 

150 grams of heavy spar are reduced with 40 grams 
wood charcoal, in the same manner as described for celes- 
tine (on page 92), and the barium sulphide obtained is de- 
composed in a litre flask, with dropping funnel and gas 
conduit tube, by means of dilute HN0 3 , filtered and 
evaporated to crystallization. Of this, or else of commer- 
cial barium nitrate, iyi kilos are gradually placed with an 



96 LABORATORY MANUAL OF 

iron spoon in a red-hot Hessian crucible, which is kept cov- 
ered with an earthen cover. After having added the whole 
quantity the closed crucible is heated for another hour at 
very high temperature. After the crucible has again partly 
cooled, remove the upper layer of the barium manganate, 
the green-colored layer of the crucible, and fill the barium 
oxide into small flasks, at once sealing them hermetically. 

The barium nitrate at first passes into barium nitrite 
and then further into barium oxide, at white heat: 

Ba(N0 3 ) 2 = Ba(N0 2 ) 2 + 20, 
Ba(N0 3 ) 3 = 13aO -{- 2N -{- 3 0. 

Barium oxide comes in grayish-white porous pieces, 
which evolve heat with water and dissolve completely in 
dilute hydrochloric acid without effervescing; this solution 
should not discolor permanganate nor blue potassium iodide 
starch paper (barium nitrate and barium superoxide). 



BARIUM CHLORIDE. 
BaCl 3 + 2H 3 0. 
a. From heavy spar. Mix together 8 parts of pul- 
verized barium sulphate, 2 parts of charcoal powder, and I 
part of common rosin. Put the mixture in a crucible and 
expose it in a blast furnace to a long-continued red heat. 
Triturate the crude barium sulphide obtained, boil about to 
of the powder with 4 times its quantity of water, and add 
hydrochloric acid until all effervescence of hydrogen sul- 
phide has ceased, and the fluid manifests a slight acid reac- 
tion. Add now the remaining to part of the barium sul- 
phide, boil some time longer, then filter, and let the alkaline 



INORGANIC PREPARATIONS. 97 

fluid crystallize. Drain the crystals, redissolve them in 
water, and crystallize again. 

b. From witherite. Pour 10 parts of water upon i 
part of pulverized witherite, and gradually add crude hy- 
drochloric acid until the witherite is almost completely dis- 
solved. Add now a little more finely pulverized witherite, 
and heat, with frequent stirring, until the fluid has entirely 
or very nearly lost its acid reaction ; add solution of barium 
sulphide as long as a precipitate forms ; then filter, evap- 
orate the filtrate to crystallization, and purify by crystal- 
lizing again. For use, dissolve I part of the barium chlo- 
ride in 10 parts of water. 

Pure barium chloride must not alter vegetable colors ; 
its solution must not be colored or precipated by hydrogen 
sulphide, nor by ammonium sulphide. Pure sulphuric 
acid must precipitate every fixed particle from it, so that 
the fluid filtered from the precipitate formed upon the ad- 
dition of that reagent leaves not the slightest residue when 
evaporated on platinum foil. 



BARIUM NITRATE. 

Ba(N0 3 ) 2 . 

Treat barium carbonate, no matter whether witherite 
or that precipitated by sodium carbonate from solution of 
barium sulphide, with dilute nitric acid free from chlorides, 
and proceed exactly as directed in the preparation of 
barium chloride from witherite. 

Solutions of barium nitrate must not be made turbid by 
silver nitrate solutions. The other tests are the same as 
for barium chloride. 



98 LABORATORY MANUAL OF 



BARIUM PEROXIDE. 
Ba0 2 . 

BARIUM PERHYDRATE. 
Ba(OH) 4 + 6H 3 0. 

A combustion tube is filled with 30 grams powdered ba- 
rium oxide, moderately heated in a combustion furnace, and a 
rapid current of oxygen dried with cone, sulphuric acid 
conducted over it. The solid peroxide, after being ground 
with a little water, is placed in 50 c. c. dil. hydrochloric acid 
which has been cooled to o° C, then the still faintly acid 
solution is filtered and allowed to flow into 500 c. c. baryta 
water which has been cooled to o° C, and saturated cold. 
The separated precipitate, consisting of glistening crystalline 
scales, is sucked dry, washed with a little ice-water, and 
preserved as paste. 

With moderate heat the barium oxide adds another 
atom of oxygen. The barium peroxide decomposes with 
hydrochloric acid: 2Ba0 3 f 4HC1 = 2BaCl 3 + 2H 3 ; the 
hydrogen peroxide with baryta: H 3 3 + Ba(OH) 3 = 
Ba(OH) 4 . 

The barium superoxide must not inflame by grinding 
with water (property of barium oxide). The value of the 
perhydrate is proven, if hydrogen peroxide is produced 
from the preparation. 



BARIUM CARBONATE. 
BaC0 3 . 
Dissolve crystallized barium chloride in water, heat to 
boiling, and add a solution of ammonium carbonate mixed 



INORGANIC PREPARATIONS. 99 

with some ammonia, or of pure sodium carbonate, as long 
as a precipitate forms ; let the precipitate subside, decant five 
or six times, transfer the precipitate to a filter, and wash 
until the wash water is no longer made turbid by silver 
nitrate solution. 

Pure sulphuric acid must precipitate every fixed particle 
from a solution of barium carbonate in hydrochloric acid. 



BARIUM DITHIONATE. 
BaS 2 6 + 2H 2 0. 

DITHIONIC AC ID. 
H 2 S 3 6 +xH 3 0. 

ioo grams finely powered black oxide manganese is elu- 
triated by mixing with water in a large mortar, decanted, 
and the remaining coarse powder again mixed with water ; 
this is repeated until the entire mineral is suspended in 
water, then allow it to settle in tall cylinders ; the water is 
removed by means of a syphon, and the black oxide of man- 
ganese brought into a liter flask with y 2 litre water. A 
current of sulphur dioxide is passed through the mixture, 
the flask being cooled with ice. When the bulk of the 
black oxide manganese has dissolved add to the solution 
which has been heated in a dish cone, barium hydrate 
solution until a filtered sample fails to yield a flesh-colored 
precipitate with ammonium sulphide. The precipitate is 
then filtered, boiled with hot water, and the combined fil- 
trates treated hot with carbonic acid until neutral. The 
barium dithionate crystallizes from the filtrate on concen- 
tion. 

Dithionic Acid. — 59 grams barium dithionate are dis- 



IOO LABORATORY MANUAL OF 

solved in water ; 20 grams of a solution of sulphuric acid 
diluted with water are added to the solution until it will no 
longer react either with sulphuric acid or with barium chlo- 
ride. After filtering off the barium sulphate the dithionic 
acid is concentrated on a flat porcelain plate in vacuum 
over sulphuric acid to a sp. gr. of 1.347. 

The peroxide withdraws from 2 molecules of sulphur- 

SO H 
ous acid two atoms of hydrogen ; 2HS0 3 H — 2H — ^ 3 tt 

The manganese salt of the dithionic acid is decomposed 
by the excess of baryta water. 

MnS20 6 + Ba(OH) 3 = BaS 2 6 + Mti(OH) 2 . 

Barium dithionate forms colorless, glossy crystals, 
which in a powdered condition lose their water of crystal- 
lization (10.81 %) at 100 C. 

Determine the percentage of barium oxide (45.96 % 
BaO) by igniting the purified salt and then weighing the 
residue of barium sulphate. 



DISTILLED MERCURY. 
Hg. 

In a combustion furnace, one end of which is lifted 
15 mm. above the other, lay a tube of hard Bohemian 
glass, both ends of which are bent downward, as shown in 
figure 8. 

The end drawn out is connected by means of a heavy 
walled, closely fitting rubber tube with a glass tube of 
medium thickness about 10 mm. outside diameter, and 
of such a length that the entire vertical tube up to the 
lower opening which turns upward is about 700 mm. The 



INORGANIC PREPARATIONS. 



IOI 



giass tube stands in a narrow glass cylinder. The other 
end of the combustion tube is bent upward somewhat 
within the furnace so that the last flame of the furnace 
stands below the highest point * of the bend of the tube. 




Fig, 8. 
From there the tube leads downward 20 cm. without re- 
duction in size ; into the end of this tube by means of a 
rubber tubing,t a second glass tube is inserted, bent hook- 
form at the bottom, which extends at least 5 cm. into the 
wider tube, and is about 80 cm. in length. To set the 

* At the point of the tube, place a loose plug of asbestos. 

f In order to have at this point a perfectly airtight connection, add the 
contrivance pictured in the small illustration on the right, which is intellig- 
ible without further explanation. The small space ^surrounding the shaded 
part) formed by a rubber stopper and a small piect; of wide glass tubing is 
filled with mercury. 



102 LABORATORY MANUAL OP 

apparatus in motion pour into the cylinder commercial 
mercury or else mercury which has become impure by use 
with other metals, and exhaust the, apparatus with a filter 
pump, adding an empty WoulrT bottle. As soon as the 
mercury has risen so high that it runs along in a thin 
stream from one end of the combustion furnace to the 
other, the rubber tubing leading to the pump is closed se- 
curely with a pinch-cock. Now the furnace is heated with 
a low flame while the mercury boils gently and distills 
through the asbestos plug. As soon as the tube leading 
downward is filled half way with mercury, open the pinch- 
cock and carefully allow air to enter the exhausted tube ; 
the mercury column now prevents air from entering this 
side of the apparatus. The apparatus works automatically, 
and the distilling mercury flows continually into a vessel 
placed below ; from time to time the quantity of mercury 
in the cylinder is replaced. 

The mercury should be 13.595 S P- S r - a ^ °° C. an d 
possess a pure silver gloss, fuse easily,- and in pouring out, 
form round regular drops leaving no threadlike residue. 
5 grams heated in a porcelain crucible should not leave a 
weighable and fusible residue. 



PURIFICATION OF MERCURY. 

Mercury can be completely freed from lead, zinc, tin, 
and other impurities by placing it in a slightly inclined 
glass tube provided with a funnel at the lower extremity, 
and aspirating a gentle stream of air through the apparatus 
for about 48 hours. The oxides of the metals collect at 
the upper end of the tube, and after about 24 hours, as a 



INORGANIC PREPARATIONS. 103 

rule, the surface of the mercury is quite clean and the 
operation is finished. Large quantities can be treated in 
this way, but mercury which has been used for amalgamat- 
ing zinc contains such a large amount of impurity that this 
method cannot be used. Silver is not removed by this 
process. 

Mercury is usually purified by shaking in a topped 
separator with cone, sulphuric acid, allowing time to 
settle and drawing off, continue until the mercury is bright 
and no longer imparts a color to the mercury.* 



MERCURIC CHLORIDE. 
HgCl2- (from residues.) 
The residues, oxydized with crude hydrochloric and 
nitric acids and then dried on the water bath are subjected 
to slow sublimation in a porcelain dish on a sand-bath with 
a large funnel set over it. Of the sublimate thus obtained 
dissolve according to its purity 1-10 to 1-5 in hot water, 
precipitate with soda lye, and grind the so obtained mer- 
curic oxide after washing and drying with the main quan- 
tity of the sublimate The acquired powder which turns 
black through the formation of mercuric oxychloride, is 
placed into a flask, covered loosely with a watch glass and 
heated on the sand bath over a small flame. The subli- 
mate gathers at the upper part of the flask in fine long 
crystals. After final sublimation remove the flask from 
the bath, break off the bottom by quickly passing over it 
a damp sponge and separate the crystals from the glass on 
a large sheet of paper with the aid of a goose quill. In 



*J. M. Crafts, Bull. Soc. Chim. 49, 856. 



104 LABORATORY MANUAL OF 

case there are poor crystals among them, they are to be 
recrystallized in four parts of boiling water. 

The crude sublimate is contaminated by other unstable 
metallic chlorides, but these are all decomposed by mer- 
curic oxide ; for instance : Fe 3 Cl e H~ 3HgO = Fe 2 03+ 3HgCl 2 . 

Pure white, rhombic prisms of mercuric chloride dis- 
solve readily without residue (calomel, iron oxide, etc.) in 
cold alcohol, ether and hot water ; heated in a test tube 
volatilize without residue. 



MERCURIC CYANIDE. 

Hg(CN) 2 . 

A diluted prussic acid solution is mixed in a flask with 
yellow mercuric oxide until the solution reacts strongly 
alkaline to litmus paper. Filter and add to the filtrate 
enough prussic acid to make the odor of it noticeable and 
so that the filtrate will react distinctly acid, then evaporate 
to crystallization. Before the mother liquor is again evap- 
orated to crystallization, add a little more prussic acid. 

Mercuric cyanide crystallizes in square columns and 
pyramids soluble in 1 1 parts of cold water and have a 
neutral reaction. Heated in small tubes, the salt develops 
cyanogen, gives a destillate of mercury drops and leaves 
black paracyanogen. 



CINNABAR. 

HgS. 
60 grams mercury are intimately mixed in a mortar 
with 23 grams flowers of sulphur until the mercury has 



INORGANIC PREPARATIONS. IO5 

entirely disappeared. Pour over this a solution of 15 
grams caustic potash in 80 c. c. water and digest several 
days at about 45° C, stirring frequently and replacing the 
evaporated water. After the mass has become of a nice 
red color, it is separated from the unaltered mercury and 
the largest part of the sulphur by elutriation, boiled with a 
solution of sodium sulphite, and washed with hot water. 

Cinnabar is a scarlet-red powder and when heated 
strongly in small tubes volatilizes without residue. 



MERCUROUS NITRATE 
Hg 2 (N 0£fr crystallized + 2H 3 0. 

Pour 1 part of pure nitric acid of 1.2 sp. gr. on 1 
part of pure mercury in a porcelain dish, and let the vessel 
stand twenty-four hours in a cool place ; separate the 
crystals formed from the undissolved mercury and the 
mother liquor, and dissolve them in water mixed with one- 
sixteenth part of nitric acid, by trituration in a mortar. 
Filter the solution, and keep the filtrate in a bottle with 
some metallic mercury covering the bottom of the vessel. 

The solution of mercurous nitrate must give with di - 
lute hydrochloric acid a copious white precipitate of mer- 
curous chloride ; hydrogen sulphide must produce no pre- 
cipitate in the fluid filtered from this, or at all events, only 
a trifling black precipitate (mercuric sulphide). 



I06 LABORATORY MANUAL OF 

MERCUROUS IODIDE. 

Hg 2 I 2 
If a saturated solution of mercurous nitrate as free as 
possible from oxide and slightly acidified with nitric acid, 
is heated to boiling with iodine, the latter becomes covered 
with a yellow powder, which partially dissolves, and the 
solution, after decantation into a warm dish, deposits in the 
dark, lustrous yellow, transparent, tetragonal scales of 
mercurous iodide ; these must be dried in the dark at or- 
dinary temperature. When the mercurous nitrate solution 
is treated with an alcoholic solution of iodine in the cold, 
small, yellow spangles of mercurous iodide are obtained, 
but the product formed by the old methods of preparation, 
by rubbing together molecular proportions of mercury and 
iodine, and adding potassium iodide in solution to a solu- 
tion of mercurous salt, have a green color, and are impure, 
although the pure yellow compound can be obtained by 
reversing the last process, and adding an excess of a dilute 
solution of mercurous nitrate to potassium iodide in solu- 
tion. The crystallized compound shows the usual color 
change, yellow at ioo° C. passing through orange to gar- 
net-red at higher temperatures. Sublimation commences 
at 1 10 to 120° C. and the salt fuses at 290 C. without de- 
composition. Towards acids and solvents, the crystallized 
compound behaves like that precipitated by potassium 
iodide ; ammonia and caustic alkalies render it green, and 
on heating convert it into the corresponding alkaline iodide 
and metallic mercury. The crystallized iodide is less 
sensitive to light than the precipitated yellow compound, 
which rapidly becomes black even in diffused daylight.* 
* A. Stroman, Ber. 20, 2818. 



INORGANIC PREPARATIONS. IOJ 



MERCUROUS BROMIDE. 
Hg 2 Br 2 . 
When mercurous nitrate solution is treated with bro- 
mine under similar conditions, small, white, nacreous, 
tetragonal scales of mercurous bromide are obtained, and 
the same compound separates in yellow, crystalline span- 
gles when an alcoholic or aqueous solution of bromine is 
used. It sublimes at 171 ° to 176 C. in small scales, is less 
sensitive to light than the iodide, dissolves in hot sulphuric 
acid with the evolution of sulphurous anhydride becomes 
black and gradually decomposes when heated with dilute 
and concentrated hydrochloric acid, dissolves slowly in hot 
nitric acid (sp. gr. 1.42), and decomposes with the forma- 
tion of the corresponding bromides when treated with am- 
monia and caustic alkalies. 



BORON. 
B. 
100 grams fused hot finely powdered borax are well 
mixed with 50 grams magnesium powder, the mass poured 
in a Hessian crucible, pressed down well and covered with 
a layer of pure borax. All these operations must be done 
rapidly and are to be carried on in warmed vessels, as the 
anhydrous borax is very hygroscopic. The crucible is 
closed with a specially well-fitting cover of strong sheet-iron 
with a rim, and heated in a Roessler's furnace for half an 
hour up to red heat. After cooling, grind the product, 
boil it with water, then with hydrochloric acid and finally 



108 LABORATORY MANUAL OF 

again with water and dry the grayish-brown powder on 
the water-bath.* 

PREPARATION OF AMORPHOUS BORON. 

Another method is to pass a current of 35 amperes 
through boric anhydride mixed with 20 per cent, of sodium 
borate and heated at 1200 , boron is liberated, but im- 
mediately recombines with oxygen with vivid incan- 
descence. 

It is well known that when boric anhydride is heated 
with the theoretical quantity or an excess of magnesium, 
reduction takes place with formation of magnesium borides. 
If the boric anhydride is in considerable excess different 
results are obtained. There are two magnesium borides, 
one unstable and decomposed by water with liberation of 
hydrogen and boron hydride, the other stable and not af- 
fected by water, hydrochloric acid, or nitric acid. 

70 grams of finely powdered magnesium free from iron 
and silicon, are intimately mixed with 210 grams of re- 
cently fused boric anhydride. The mixture is heated to 
bright redness in a clay crucible, and in a few minutes an 
energetic reaction takes place. The central part of the 
product is boiled with water and hydrochloric acid until 
the magnesium borate is removed, then treated for a long 
time with successive quantities of pure boiling hydro- 
chloric acid, washed with water, treated with alcoholic 
potash, again washed with water, boiled for several hours 
with hydrofluoric acid, washed with water, and dried in a 
vacuum. The product is a very light maroon powder 
which does not alter when exposed to air ; it contains 94 to 



* Gattermann, Ber. 22, 195. 



INORGANIC PREPARATIONS. IO9 

95 per cent, of boron, 2.3 to 3.75 per cent, of magnesium 
and 1.2 to 1.6 per cent, of insoluble matter. 

If this product is fused with 50 times its weight of boric 
anhydride, and the product treated in the same way as the 
original product, a maroon powder is obtained containing 
only traces of magnesium. 

One product contained boron, 98.30 ; magnesium, O.37; 
insoluble, 1.18 = 99.85. 

If the boron is required perfectly free from nitride, re- 
duction must be affected in a crucible brasqued with a mix- 
ture of finely powdered titanic oxide and carbon ; the 
product contains from 92.6 to 99.2 per cent, of boron. 
Boric anhydride may also be reduced by magnesium in 
porcelain dishes in an atmosphere of hydrogen, and a very 
pure product obtained, but the yield is small.* 

It can also be prepared by mixing 3.5 grams of boric 
anhydride and 1 1 grams of calcium fluoride by gently 
heating with cone, sulphuric acid ; the boron fluoride 
evolved is passed over heated potassium contained in a 
series of bulbs. Potassium fluoride and boron are formed 
and easily separated by washing with water. Amorphous 
silicon may be prepared in a similar manner. t 



BORAX. 

Na 2 B 4 7 . 

An intimate mixture of well-ground common salt and 

boric acid is introduced into an acid-proof, tubulated clay 

retort, and heated to slightly above a low red heat, when 

sufficient superheated steam is admitted through the tu- 

* By H. Moissan, Compt. rend., 114, 392—397. 
f S. G. Rawsox, Chem. News, 58, 283. 



[IO LABORATORY MANUAL OF 

bulature to condense the hydrochloric acid, which is evolved, 
the acid being collected in a cooled receptacle attached to 
the retort neck. Ultimately anhydrous borax only is left 
in the retort, and this is thrown, while still hot, into cold 
water and crystallized.* 



BORACIC ACID. 
H3BO3. 

200 grams powdered borax are dissolved in one-half 
litre of boiling water, and 300 c. c. dil. hydrochloric acid 
added. After expiration of a day suck the separated scaly 
crystals dry on the platinum cone, wash them with a very 
little water, and recrystallize once from water. 

The white, pearl-like crystals must dissolve in 6 parts 
alcohol and 25 parts cold water and on heating, after 
evaporation of the water, melt to a colorless gla^s which 
when cooled remains transparent. The watery solution 
reddens litmus paper ; if turmeric paper strips are saturated 
with it and dried in a warm place, the yellow color will be 
changed to an orange-brown, which with alkaloids be- 
comes greenish-black. The impurities usually present are 
hydrochloric and sulphuric acids. 



SILICON. 

Si 

Amorphous silicon is readily obtained by the action of 

magnesium on silica, provided that the materials are quite 

dry, and that the action is moderated by the presence of 

magnesium oxide. In absence of the ox4de, the tempera- 

* By H. N. Warren, Chem. News, 67, 244-245 



INORGANIC PREPARATIONS. Ill 

ture of the reaction is too high, and some of the silicon is 
fused. Silica is not so satisfactory as magnesia for this 
purpose. Powdered quartz and magnesium powder such 
as is used for photographic purposes are mixed in the cal- 
culated proportions, and to the mixture is added one-fourth 
of its weight of calcined magnesia. The three substances 
are very intimately mixed and placed in a fire-clay cruci- 
ble, which they must not more than half fill. A layer of 
magnesia is placed on the top, and the crucible is then 
heated at 149 to 205 ° C. in order to thoroughly dry the con- 
tents. The crucible with its cover is then heated to red- 
ness for a few minutes, and as soon as the action ceases it 
is allowed to cool. Reduction takes place at 282 C. If 
the mixture is placed on a plate and covered with mag- 
nesium powder, and the latter is ignited, reduction spreads 
throughout the mass. 

The product is heated with hydrochloric acid, then 
with boiling sulphuric acid, then two or three times alter- 
nately with hydrofluoric acid and sulphuric acid, and, 
finally, with hydrochloric acid. After drying, the silicon 
forms a maroon colored, homogeneous powder, containing 
only 1.0 to 0.4 per cent, of impurities. Any small globules 
of fused silicon can, if necessary, be removed by levigation.* 

Another method is to heat 40 grams of finely pow- 
dered sand with 10 grams of magnesium in not too 
thin a test tube, the whole tube is heated first mod- 
erately, and then a small portion is heated strongly, 
beginning at the lower end and continuing up- 
wards. The product is grayish-black. The frag- 
ments of the tube, after the substance has been taken out, 

* By ViGOURON, Compt. rend., 1835, 120, 94. 



112 LABORATORY MANUAL OF 

should be treated with acid, as the adherent substance will 
decompose in moist air and evolve silicon hydride. Silicon 
is obtained by heating the substance in a closed crucible 
with zinc ; on dissolving out the zinc, it is obtained in steel- 
blue needles.* 

It can also be prepared by introducing aluminium, 
in pieces the size of a walnut, into a clay crucible 
containing a fused mixture of 4 parts of potassium 
silico-fluoride, 1 part of potassium chloride, and 2 
parts of potassium carbonate, and when the violent 
reaction has subsided, the mass is heated to whiteness for 
five minutes. When cool, the crucible is smashed; the 
button, carefully detached from adhering slag, is placed in 
a plumbago crucible with 12 parts by weight of aluminium 
and 2 of tin, and covered with a layer of sodium silicate, 
the mixture is submitted for two hours to the strongest 
heat obtainable. When cold, the piece of aluminium is 
broken, when the new modification of silicon is found in 
large, lustrous, infusible, oblique octahedra, insoluble in all 
acids except hydrofluoric, t 

Still another method is as follows : Small bars of 
" silicon-eisen " are suspended in dilute sulphuric acid 
from the positive pole of a battery of two ferric 
chloride cells and are in contact with a platinum 
plate forming the negative pole. The iron dissolves and 
leaves a residue of graphite, silica, and amorphous silicon, 
which is heated to redness in a stream of carbonic an- 
hydride, and then to a full red heat in a closed iron 
tube with some zinc ; the zinc button obtained in this 



*L. Gattermann, Ber. 22, 186. 

f By H. N. Warren, Chem. News, 67, 136-137. 



INORGANIC PREPARATIONS. 113 

manner is dissolved in hydrochloric acid, when crystal- 
line silicon remains insoluble ; by heating the amor- 
phous silicon at a full white heat with aluminium instead 
of zinc, graphitoidal silicon is obtained. When an alloy 
of aluminium and silver is heated to an intense white 
heat with potassium silicofluoride, small quantities of 
silicon are produced in the form of a bright reddish- 
brown powder.* 

CRYSTALLINE SILICIC ACID. 
H 2 Si0 3 . 

Silicious limestone is treated with crude concentrated 
hydrochloric acid until carbonic anhydride ceases to be 
evolved, filter and add to the filtrate 29 to 31 per cent, 
hydrochloric acid until a cloudiness appears. After re- 
maining 24 hours the solution is decanted, the precipi- 
tate strained and washed, finally with distilled water and 
then dried on porcelain. Silicic acid so obtained is 
crystalline and corresponds to the formula H 2 Si0 3 +3H 2 
or H 2 Si0 3 + 2H 2 0. It is more soluble than the amor- 
phous variety, t 

SILICON CHLORIDE. 

SiCl 4 . 
Take a hard glass tube 2 m.m. wide, fill it half way 
with the crude amorphous silicium as described above, 
lay it horizontally in a combustion furnace and at mod- 
erate heat, lead a current of dry chlorine over it. 



* H. N. Warren, Chem. News, 57, 54. 
f H. Hager, Pharm. Centralb. 29, 115. 



114 LABORATORY MANUAL OF 

The distilling silicon chloride is condensed in a receiver 
which is surrounded by a freezing mixture of ice and com- 
mon salt, while the surplus chlorine is absorbed in soda 
lye. The greenish product is shaken with a little mercury, 
and then distilled from the water- bath with a thermome- 
ter and condenser attached. 

Si +4CI = SiCl 4 . The free chlorine dissolved in the 
silicon chloride is removed by shaking with mercury. 

The silicon chloride should boil at 58 to 6o° C. and 
appear as a colorless, mobile liquid fuming strongly when 
exposed to the air, it is decomposed by water with separa- 
tion of hydrated silicic acid : 

SiCl 4 + 4H 3 = Si(OH) 4 + 4HC1. 



CHLORIDES OF SILICON, ALUMINIUM, ETC. 

Iron alloys of silicon or aluminium are heated to red- 
ness in a clay crucible, and a current of chlorine gas is 
passed into the mass, suitable means being adopted to col- 
lect the volatile products. With chlorine and silicon-iron, 
the ferric chloride is condensed first, then the silicon 
chloride ; if hydrogen chloride is used instead of chlorine, 
the ferrous chloride formed remains in the crucible and 
silicon chloroform distills off. The aluminium chloride ob- 
tained from aluminium iron is purified by mixing with iron 
borings and distilling, or if the aluminium iron alloy is 
mixed with common salt previous to submitting it to the 
action of chlorine, a sublimate of aluminium sodium 
chloride is obtained. 



* By H. N. Warren, Chem. News, 60, 158. 



INORGANIC PREPARATIONS. 1 1 5 



PREPARATION OF SILICON AND ALUMINIUM 
CHLORIDE. 

Silicon chloride, mixed with but little ferric chloride 
and readily purified by redistillation, is obtained by pass- 
ing chlorine "into siliconeisen, containing 15 per cent, of 
silicon, heated to redness in a tubulated clay retort, and 
retaining the less volatile ferric chloride in the upper 
part of a suitable adapter, while the lower part is cooled 
in a freezing mixture to condense the silicon chloride. By 
using hydrochloric acid gas instead of chlorine, ferrous 
chloride, and the more volatile silicon-chloroform, SiHCl 3 , 
are obtained. 

By the action of chlorine on an alloy of iron with 10 
per cent, of aluminium, aluminium chloride is produced, 
which can be purified by distillations from iron borings. 
When the pulverized alloy is previously mixed with sodium 
chloride, the passage of chlorine gives rise to the sublima- 
tion of aluminium sodium chloride. 



ALUMINIUM H Y D R AT E. 
Al :( O H )e, from Cryolite. 
50 grams cryolite are finely powdered, then thoroughly 
mixed with 50 grams calcinedinarble and ignited for half an 
hour in a platinum crucible placed in Roessler's furnace. 
The powdered melt is boiled with water, possible traces of 
calcium removed from the filtered solution by a few drops 
of soda solution and then precipitated hot with carbonic 



H. N. Warren, Chem. News, 66, 113-114. 



Il6 LABORATORY MANUAL OF 

acid. The separated aluminium hydrate is washed by de- 
cantation with a good deal of hot water, collected, dried 
on the water bath, and if desired, transformed into an- 
hydrous aluminium sesquioxide by ignition. The nitrate 
when evaporated, leaves pure sodium carbonate. 

The aluminum sodium fluoride is decomposed by 
caustic lime, forming sodium aluminate soluble in water : 

Na d Al 3 Fi 3 + 6CaO = Na 6 Al 3 6 + 6CaF 3 . 

The sodium aluminate is decomposed by carbonic acid : 

2Na 6 Al 3 6 + 6H 3 C0 3 = 2Al 3 (OH) e + 6Na 3 C0 3 . 



REDUCTION OF ALUMINIUM OXIDE. 

A1 3 3 . 
Two parts of pure, finely powdered aluminium oxide 
is made into a paste with one part of petroleum or some 
other hydro-carbon, and then mixed with one part of sul- 
phuric acid. When the mass is homogeneous with a pale 
yellow tint, and begins to give off sulphurous anhydride, it 
is wrapped in paper and thrown into a crucible heated to 
above 8oo° C. in order to decompose the hydrocarbon. The 
compact product thus obtained is powdered and mixed 
with its own weight of a finely divided metal, the mix- 
ture being then heated to a white heat in a plumbago 
crucible. The regulus after being allowed to cool is found 
to contain grains of an aluminium alloy in the midst of a 
metallic powder. This method of reduction is applicable 
to silica, calcium oxide, magnesium oxide, etc.* 



G. A. Faurie, Compt. Rend. 105, 494. 



INORGANIC PREPARATIONS. 117 



ANHYDROUS ALUMINIUM CHLORIDE. 

AloCl 6 . 
Dry hydrogen chloride extracts the whole of the alum- 
inium from an alloy of copper and aluminium without at- 
tacking the copper. The reaction is most energetic a 
little below a red heat. The alloys containing 15 to 40 
per cent, of aluminium are best powdered, mixed with 
powdered charcoal (to prevent the fusion of the remaining 
copper), put into a graphite retort, and when heated just 
below a red heat a current of hydrogen chloride is passed 
through. The aluminium chloride distills over, and may 
be condensed in suitable vessels, the liberated hydrogen 
passing on. 



FORMATION OF ULTRAMARINE IN THE 
WET WAY. 

The material used is washed kaolin, with the fol- 
lowing percentage composition: Silica, 46.83; alumina, 
40.25; water, 12.60; potash, 0.37; lime, trace; total, 
100.05 ; and was expressed by the formula: 

2Si0 3 : 1.997 A1 3 3 :: 1.79 H 2 0. 

The ultramarine mixture is made in the proportion — 
Washed kaolin, 100 parts ; anhydrous sodium carbonate, 
IOO parts ; sulphur, 60 parts. The mixture is heated in 
small porcelain crucibles, holding 15 to 20 grams of the 
mixture; this is pressed in, and the top covered to a 



*By C. F. Mabery, Ber. 22, 2658. 



Il8 LABORATORY MANUAL OF 

depth of 5 to 6 mm. with powdered charcoal, and the cruci- 
ble then heated with the lid on. The mixture, after heat- 
ing and separation from the charcoal, gives on digestion 
with solution of liver of sulphur, the deep blue of ultra- 
marine. Kaolin, digested alone with liver of sulphur solu- 
tion, is unchanged.* 



HYDROGEN BROMIDE. 
HBr. 

ioo grams benzole and a few grams of anhydrous fer- 
rous bromide are placed in a dry two-necked bottle and 
135 c. c. bromine allowed to drop in from a dropping fun- 
nel with long fine stem. The Woulff bottle is placed in 
cold water during the first half of the operation, in order 
to control the vigorous heating and volatilization of the 
benzole which takes place. The gas is passed through a 
small tube charged with anhydrous ferrou bromidet then 
through one charged with anthracene and now forms pure 
hydrogen bromide. For the production of cone, aqueous 
hydrobromic acid, the gas is led into a small bottle, by de- 
grees small quantities of water are added with a wash-bot- 
tle and cooled with a freezing mixture of ice and common 
salt. The saturated solution is preserved in a well stoppered 
bottle with cap and kept in a dark place. 

C 6 H 6 +4Br = C 6 H 4 Br 2 + 2HBr. 

The small quantity of ferrous bromide (FeBr 2 ) acts as 



* By F. Knapp, J. pr. Chem. [2] 32, 375-39°- 

f Produced by mixing 25 grams ferrous FeBr 2 bromide with 3 c. c. bro- 
mine in the cold. 



INORGANIC PREPARATIONS. II9 

the transferrer of bromine. The hydrogen bromide, devel- 
oped in a very regular stream, carries off benzole-vapors 
which bromate in the ferrous bromide tube and are held 
back. The gas is freed by the anthracene from the slight 
traces of free bromine. 

The aqueous solution should be entirely colorless, fume 
strongly when exposed to the air, and have a sp. gr. of at 
least 1.78 (at o Q C. saturated acid). 

Another method : — A mixture of 1 part of red phos- 
phorus, 2 parts of water, and sufficient sand to form a 
paste, is introduced into a flask, 10 parts of bromine then 
gradually added by means of a funnel provided with 
a stopcock, the flask gradually warmed, and the mixture 
of hydrogen bromide and bromine vapor passed through a 
deep glass jar filled with a mixture of red phosphorus and 
asbestos, impregnated with concentrated hydrobromic acid. 
Every trace of bromine vapor is thus effectually retained, 
and the process is continuous and requires no supervision 
beyond an occasional shaking of the flask.* 

By means of the following arrangement, a large quan- 
tity of bromine can be rapidly converted into hydrobromic 
acid : A glass tube, 7 inches long and ^ inch in diameter, 
is fitted at each end with a cork carrying a piece of small 
tubing and a piece of stout wire. The ends of these pieces 
of stout wire, within the longer tube, are joined by a spiral 
of platinum wire 1 inch long, and after expelling the air 
the spiral is heated to bright redness by an electric current ; 
a stream of hydrogen, impregnated with bromine by bub- 
bling through that liquid, which maybe heated at 60 ° C, is 
passed through the longer tube, and, as long as a slight 



* M. Fileti and F. Crosa, Gazetta, 21, 64. 



120 LABORATORY MANUAL OF 

excess of hydrogen is maintained, hydrobomic acid quite 
free from bromine issues from the other end, and is col- 
lected in water. There is very little danger from explo- 
sion, but to render it impossible, the small supply tube may 
be plugged with a little glass wool.* 

A convenient method of preparing hydrogen bromide 
in quantity is to drop strong sulphuric acid from a tap 
funnel on solid potassium bromide heated in a stoppered, 
tubulated retort on the water-bath. The gas given off is 
contaminated with small quantities of sulphurous anhy- 
dride and bromine, from which it is freed by two sets of 
wash-bottles, the first of which contains a strong solution 
of bromine in hydrobromic acid, the second, amorphous 
phosphorus suspended in hydrobromic acid. When all 
the sulphuric acid has been added, and the evolution of 
gas has slackened, the retort may be heated over a flame. 

Another method is to pass sulphurous anhydride 
through a solution of bromine (i vol.) in concentrated 
hydrobromic acid (i vol.). The evolved hydrogen bro- 
mide is then purified as above. f 

Hydrogen bromide may also be prepared by adding 
bromine (385 grams) to a mixture of liquid paraffin (500 
grams) and dry phosphorus in small pieces ^o grams ; 
water (about 100 grams) is then gradually run in and the 
evolved gas purified by passage over moist phosphorus.J 

This method, proposed for the preparation of hydro- 
bromic acid, is based on the fact that the action of 
gaseous hydrogen sulphide on liquid bromine with forma- 



*G. S. Newth, Chem. News, 64, 215. 
\ E. Leger, Compt. rend. 115, 946-948. 
tA. Gassman, Chem. Centr. 1893, i., 77 1 * 



INORGANIC PREPARATIONS. 121 

tion of gaseous hydrogen bromide and solid sulphur de- 
velops + 144 cal., without taking into account the heat 
developed by the combination of the sulphur with the 
excess of bromine. 

Hydrogen sulphide is bubbled through a layer of 
bromine contained in a tall, narrow vessel, and covered 
by a layer of water or hydrobromic acid. The gas passes 
into a second flask which contains a solution of potassium 
bromide in hydrobromic acid holding a small quantity of 
red phosphorus in suspension, and the gas which issues 
from this flask contains neither bromine vapor nor hydro- 
gen sulphide. The current of hydrogen bromide is con- 
trolled by regulating the current of hydrogen sulphide. 
The latter gas should be made in a " continuous " 
apparatus.* 

Although concentrated sulphuric acid decomposes po- 
tassium bromide with liberation of bromine, when a more 
dilute acid is used there is no evolution of bromine. To 
obtain pure hydrobromic acid, 150 c. c. of sulphuric acid 
of 1. 41 sp. gr. is poured on to 100 grams of coarsely pow- 
dered potassium bromide, and the mixture warmed gently 
and shaken until the salt is dissolved. The liquid is then 
submitted to distillation ; it begins to boil at about 126 C, 
and the temperature slowly rises to 150 C, at which point 
almost the whole of the hydrobromic acid passes over; then 
the temperature rapidly goes up to 200 C, and traces of 
sulphuric acid are mechanically carried over. The process is 
now stopped, as between 200 and 250 C. only small quan- 
tities of hydrobromic acid, mixed with a little sulphuric 
acid, pass over. The distillate is redistilled, collecting only 



A. Recoura, Compt. rend., no, 784. 



122 LABORATORY MANUAL OF 

what passes over at 126 C. ; this has a specific gravity of 
1.49, contains 48 per cent, of HBr, is colorless, and con- 
tains neither sulphuric acid, sulphurous acid, nor bromine. 
150 grams of bromide yield about 200 grams of acid. If 
the bromide contains bromate, the receiver is changed when 
the distillate become colorless ; the acid thus obtained con- 
taining bromine is treated with a little sodium sulphite, and 
rectified with the rest. Gaseous hydrobromic acid may be 
obtained by distilling the solution containing 48 per cent, 
from anhydrous calcium bromide.* 



HYDROGEN IODIDE. 
HI. 

In preparing hydrogen iodide from iodine and amorphous 
phosphorus the iodine is placed in a flask provided with a 
bent neck and connected with the vessel containing the phos- 
phorus and water by means of a bent tube. By turning 
the flask round the bent tube, fresh quantities of iodine 
can be added when requisite without admitting air into 
the apparatus. t 

Another method of preparation is to moisten 100 parts 
of iodine contained in a retort with about 10 parts of water. 
The retort is then fitted with a funnel closed with a glass 
rod, containing 5 parts of amorphous phosphorus mixed 
with 10 parts of water. One drop of water containing phos- 
phorus is let into the retort ; more phosphorus is slowly 



*By W. Feit and K. Kubierschky, J. Pharm. [5], 24, 159; from 
Pharrn. Zeit. Russ., 30, 298. 

f A. Etard, Bull. Soc. Chim. 49, 742. 



INORGANIC PREPARATIONS. 123 

added, after which large amounts may be used. The mix- 
ing is complete in 15 minutes. If more than a drop is 
added at first the action cannot be controlled, and will 
generally result in a violent explosion. No heating is 
necessary. The iodine carried over by the hydrogen 
iodide is nearly all deposited in the neck of the retort, 
which is inclined upward. By using 100 grams of iodine, 
5 grams of phosphorus and 25 c. c of water, 95 grams 
of hydrogen iodide (of which 37.5 grams were obtained by 
distillation) are obtained, instead of 100.8 grams. With 
20 grams of water 98.1 grams are obtained (74.4 grams 
as gas and 23.7 grams by "distillation).* 



IODINE PENTOXIDE. 
I2O5. 

30 grams iodine are placed in a retort and 158 c. c. 
of water and nitric acid free from nitrogen oxides (page 18) 
poured over it. On shaking a reaction takes place which 
is hastened by moderate heating. The red vapors are 
driven out by a strong current of air, which is blown into 
the tubulature of the retort through a glass tube. In spite 
of this a part of the iodine is invariably reduced by these 
nitrogen oxides ; it volatillizes and is condensed with the 
distilling acid in a receiver, which is kept cool. At inter- 
vals the heating is stopped and the distillate, after having 
air blown into it, is put back. The white residue is dis- 
solved in a little water and evaporated to dryness in a 
porcelain dish, iodic acid anhydride remaining in white 
crystals. 

* H. I. L. Meyer, Ber. 20, 3381. 



124 LABORATORY MANUAL OF 



IODINE TRICHLORIDE. 

IC1 3 . 

20 grams iodine are gently heated in a small retort, the 
bent neck of which terminates in a weighed balloon filled 
with chlorine and closed, but connected with a Kipp's 
chlorine apparatus. As soon as the iodine vapors enter 
the balloon a strong absorption of chlorine takes place, and 
iodine chloride precipitates against the walls in reddish- 
yellow crystals. Finally dry carbonic acid is led through 
to drive out the surplus chlorine. Any particles which 
cannot be removed from the balloon mechanically are dis- 
solved in ten times their weight of water, and preserved as 
iodine chloride solution. 

Iodine trichloride is an orange-colored pungent crys- 
talline powder, readily soluble in water to a clear yellow 
liquid. Chloroform should not remove iodine from the 
aqueous solution until a little stannous chloride has been 
added. On heating, the iodine trichloride should change 
without leaving any residue into brown vapors, which con- 
dense again to an orange- colored sublimate. 



HYDROCYANIC ACID. 

HCN. 

500 grams coarsely powdered potassium ferricyanide are 
distilled on the gas stove in a well ventilated place, with a 
mixture of 3 50 grams cone, sulphuric acid and 700 c. c. water. 
With the condenser two Woulff bottles are connected; these 



INORGANIC PREPARATIONS. 1 25 

stand on ice ; the vapors escaping from the last bottle are 
led into cold water. The insoluble residue* forming in the 
retort causes a slight jolting of the contents, but by heat- 
ing uniformly and carefully no danger need be feared. 
The distillate is almost pure. If absolutely anhydrous 
hydrogen cyanide is required, fill the first of the Woulff 
bottles before distillation half-way with porous calcium 
chloride, and at the conclusion set it in warm water, in order 
to distill its contents into the second bottle. The product 
should not be preserved in an anhydrous, but in a diluted 
condition ; the aqueous hydrocyanic acid keeps still better 
if one drop of diluted mineral acid is added to every 100 
c. c. 

The anhydrous hydrocyanic acid is a very volatile, 
colorless liquid, which when brought in contact with the 
skin produces a cold feeling, like evaporated ether. It 
boils at 27 C. and crystallizes in a freezing mixture. The 
aqueous solution does not redden litmus paper, f 



PURIFICATION OF HYDROFLUORIC ACID. 

HF. 
The apparatus employed for distilling commercial hy- 
drofluoric acid consists of a heavy sheet-lead retort, 6 inches 
high and 4 inches in diameter, with a rim at the top formed 
by beating the lead over an iron ring 1 inch deep and ^ 
inch thick ; the lid is of J^ inch iron plate, covered with 
lighter sheet lead, and is fixed down by a screw working in 
a socket in an iron bridge, which is secured to projections 



* This residue may be used in the preparation of Berlin Blue. 
f Wohler, Annalen, 73, 219. 



126 LABORATORY MANUAL OF 

on the opposite sides of the iron ring of the rim. A washer 
of india-rubber is placed between the cover and the rim. 
The leaden nose of the retort points upwards, and is con- 
nected by india-rubber tubing to a Liebig condenser, the 
inner tube of which is of thin india-rubber. The retort is 
charged through a funnel with 25 per cent, hydrofluoric 
acid, which yields a distillate of convenient strength for 
analytical work. The first portions of the distillate con- 
tain silicate and are discarded, whilst any sulphur is re- 
moved by filtration.* 



STANNOUS CHLORIDE. 

SnCls, Crystallized + 2H 2 0. 

Reduce grain tin to powder by means of a file, or by 
fusing it in a small porcelain dish, removing from the 
fire, and triturating with a pestle until it has passed again 
to the solid state. Boil the powder for some time with 
concentrated hydrochloric acid and a few drops of platinic 
chloride in a flask (taking care always to have an excess of 
tin in the vessel) until hydrogen gas is scarcely evolved ; 
dilute the solution with 4 times the quantity of water 
slightly acidulated with hydrochloric acid, and filter. Keep 
the filtrate for use in a well-stoppered bottle containing 
small pieces of metallic tin, or some pure tin-foil If these 
precautions are neglected the stannous chloride will soon 
change to stannic chloride, with separation of white oxy- 
chloride, which will render the reagent unfit for use. 



* By R. Hamilton, Chem. News, 60. 252. 



INORGANIC PREPARATIONS. 1 27 

A solution of stannous chloride must, when added to 
excess of solution of mercuric chloride, immediately pro- 
duce a white precipitate of mercurous chloride ; when treated 
with hydrogen sulphide it must give a dark brown pre- 
cipitate ; it must not be precipitated nor rendered turbid 
by sulphuric acid. 

ANHYDROUS STANNOUS CHLORIDE. 

SnC ! 2 . 

Commercial stannous chloride is heated slowly on the 
gas stove ; the salt melts in its water of crystallization, then 
becomes pasty, and gradually entirely solid. The dehy- 
drated salt is fused once more, and in cooling it is 
placed in a mounted retort of hard Bohemian glass, the 
upper part of which is covered with a cap of wire gauze or 
asbestos, to avoid too strong radiation, and distilled as 
quickly as possible into a porcelain dish, which is kept 
covered with a second dish. As the stannous chlo- 
ride boils at about 327 C. the heat must be very 
strong ; a small blow-pipe furnace will serve as the best 
source of heat. The neck of the retort is heated with a 
Bunsen burner, so it will not choke up with the solidifying 
distillate 

Anhydrous stannous chloride is a white, crystalline 
mass, melting at 250 C; dissolving readily in water, alcohol, 
ether and soda lye. 

ANHYDROUS STANNIC CHLORIDE. 
SnCl 4 . 
150 grams pure tin (granulated or in bars) are heated 
to fusion on the gas stove in a mounted, tubulated retort, 



128 LABORATORY MANUAL OF 

and a strong stream of dry chlorine led into it through a 
glass tube opening near the surface of the fused metal. 
The retort connects with a very long condenser and two 
WoulrT bottles as receivers. The receivers are placed in 
ice- water, to hasten the condensation of the very volatile 
chloride. The chloride collected is distilled from a frac- 
tional distilling flask containg a little tinfoil. 

Sn + 4C1 = S11CI4. The free chlorine combines with 
the metallic tin during the rectification. 

Anhydrous stannic chloride is a colorless solution, 
boiling at 114 C, fuming strongly when exposed to air, 
of 2.278 sp. gr. at o° C, with a small amount of water, it 
furnishes crystalline compounds, but dissolves completely 
in a larger quantity of water. 



PHOSPHORUS 

FROM 

PHOSPHATES OF THE ALKALIES AND ALKA- 
LINE EARTHS BY MEANS 
OF ALUMINIUM. 

When sodium metaphosphate is heated with aluminium 
in a current of hydrogen, 28 to 31 per cent, of the phos- 
phorus distills over, and a residue is obtained consisting of 
alumina, sodium aluminate, and aluminium phosphide. All 
the phosphates of calcium and magnesium, when heated 
with aluminium, yield phosphorus. 

Aluminium phosphide, AljP 5 is obtained by heating 
aluminium in phosphorus vapor, and then heating the 
product until phosphorus ceases to come off. It is a gray 
crystalline powder. 



INORGANIC PREPARATIONS. 1 29 

The whole of the phosphorus in the phosphates may 
be obtained by adding silica to the mixture in the propor- 
tions represented by the equation : 

3Ca(P0 4 ) 3 + 10A1 + 3Si0 3 = 3CaSi0 3 + 5A! 3 3 + 3P 2 . 

When a mixture of calcium metaphosphate and calcium 
sulphate is heated with aluminium, a violent explosion 
ensues. It has been found that this is due to the sulphate. 
Barium sulphate or calcium sulphate, when heated with 
aluminium, act with explosive violence and sulphur is set 
free. The chlorides are also decomposed by aluminium at 
a high temperature.* 



PURE PHOSPHORIC ACID FROM SODIUM 
PHOSPHITE. 
H3PO4. 
Crystals of hydrogen sodium phosphate are subjected 
to the action of gaseous hydrogen chloride. In this man- 
ner syrupy phosphoric acid in amount corresponding with 
a yield of 75 per cent, of the theoretical quantity is 
obtained, f 

Pure phosphoric acid may also be obtained when pow- 
dered calcium phosphate is added gradually to a slight 
excess of commercial hydrofluoric acid diluted with an 
equal volume of water, and contained in a leaden or plati- 
num vessel. There is considerable development of heat, 
and the liquid must be thoroughly agitated. When the 



*A. Rossel and L. Frank, Ber. 27, 52. 
f G. Watson, J. Soc. Chem. Ind. 2, 224. 



130 LABORATORY MANUAL OF 

action moderates, the liquid is gently heated, water being 
added to make up for loss by evaporation. When the 
liquid becomes viscous, the excess of hydrogen fluoride 
begins to escape, and the mixture is then heated until the 
expulsion of the acid is complete. The syrupy liquid thus 
obtained contains from 60 to 70 per cent, of phosphoric an- 
hydride in the form of orthophosphoric acid. With pure 
materials, the phosphoric acid obtained is very pure ; if 
bones and ordinary acid have been used the product must 
be heated to carbonize the organic matter, dissolved in 
water, filtered, and again evaporated. Pyrophosphoric and 
metaphosphoric acids can be obtained by evaporating at 
higher temperatures.* 

Another method is to heat 127 grams white phosphor- 
us with 1400 c. c. nitric acid (1.20 sp. gr.) in a retort with 
receiver. The phosphorus melts, and then the operation 
quietly proceeds. At intervals the distillate must be poured 
back. When the phosphorus has passed entirely into solu- 
tion (after 10 to 12 hours) it is evaporated in a platinum 
dish until a sample taken out with a glass rod together with 
cone, sulphuric acid and ferrous sulphate solution ceases to 
give a reaction for nitric acid. The temperature must not 
exceed 188 C. The acid when mixed with mercuric chlor- 
ide solution must show no trace of phosphorus acid. After 
this, it is treated warm with sulphureted hydrogen until on 
standing there is no further precipitate of arsenic sulphide, 
then diluted with a little water, filtered, and again slowly 
evaporated, until a thermometer dipped into it shows 
160 C. 



* M. Nicolas, Compt. rend., in, 974. 



INORGANIC PREPARATIONS. 131 

The acid should show a sp. gr. of 1.88, and be free 
from arsenic and phosphoric acid. 



PHOSPHORUS TRISULPHIDE. 
P2S3. 
310 grams red phosphorus are mixed with 480 grams 
powdered sulphur and the powder poured by spoonfuls 
into a hessian crucible which has been heated on a Bunsen 
burner. After adding each portion, the crucible is closed 
with a cover whereupon the reaction should take place at 
once. When the whole mixture has been added, the cruci- 
ble is allowed to cool sufficiently to leave the mass soft, 
and then the phosphorus sulphide is poured out on a piece 
of sheet-iron. The solid product is broken in pieces while 
warm and placed in a well-stoppered bottle. Phosphorus 
trisulphide forms in a hard, gray, easily powdered mass, 
which when exposed to air becomes moist and smeary, de- 
veloping sulphureted hydrogen. 



CALCIUM PHOSPHITE. 
CaP. 

To a strong clay crucible, about 6]/ 2 cm. wide and 12 
cm. high, fit a round cover of sheet-iron 2 mm. thick pro- 
vided with a round opening in the center of 2.5 mm. 
diameter and into which is fitted an iron tube 30 cm. long. 
At the upper end of this iron tube, a thin walled glass 



132 LABORATORY MANUAL OF 

tube of 1 5 cm. in length is fastened.* Fig. 9. After having 
placed the iron tube perpendicularly in the crucible, the 
latter is filled with 100 grams burnt marble or lime in 
pieces the size of a hazel nut. Cover the cruci- 
ble and then heat in Roessler's annealing furnace. 
When the crucible has become red-hot, 65 grams 
of dry phosphorus in sticks are dropped into it 
through the glass tube, in pieces of about 5 to 10 
grams. Immediately upon dropping each piece 
of phosphorus the glass tube is closed with a 
cork provided with a handle. The influence of 
phosphorus on the lime is manifested each time 
by the escape of a little phosphorus pentoxide 
in form of a white cloud of smoke from the 
chimney of the furnace. If this reaction fails 
to take place, the iron tube is raised a little, 
allowing the phosphorus to enter into the cruci- 
ble. While at first only minimum quantities 
escape reaction, the conclusion of the operation 
fig. 9. j g s i lown by t} ie appearance of thick smoke. 
The flame is then extinguished, the crucible taken out, and 
the product immediately upon having cooled (still slightly 
warm) is filled into a well-closed specimen cylinder. 

7CaO f 7P = Ca 3 P 3 7 + 5CaP. Calcium phosphide 
forms in dark, hard, rainbow-colored pieces, which when 
thrown into warm water develop phosphureted hydrogen : 
2CaP + 4H 3 = 2Ca (OH) 2 + P2H4. + 

* For this purpose wind a little thin asbestos cord around the glass tube, 
then twist it into the iron tube, after having moistened the asbestos with 
water glass. The joints are covered with a pasty mixture of powdered 
oxide manganese and water glass, then dried at moderate heat. The glass 
tube must be sufficiently wide to conveniently allow the passage of the 
phosphorus sticks. 

|Gattermann and Haussknecht, Ber. 23, 1175. 




INORGANIC PREPARATIONS. 1 33 



PHOSPHORUS OXY FLUORIDE. 

Zinc carbonate is dissolved in excess of hydrofluoric 
acid, the solution evaporated, and the zinc fluoride dried 
at 300 and placed in a brass tube, to which a bromine 
burette, containing slight excess of the calculated quantity 
of phosphorus oxychloride, and a leaden delivery tube are 
adapted by a paraffined cork. The leaden tube is connected 
to another brass tube cooled by a freezing mixture to 20° C, 
and this leads to another tube containing zinc fluoride, 
which removes any traces of oxychloride escaping from 
the oxyfluoride. The phosphorus oxychloride is dropped 
slowly on to the zinc fluoride, the ensuing reaction being 
assisted by warming carefully at 40 to 50 C, and the 
evolved gas is collected over mercury in glass vessels.* 



HYDROGEN PHOSPHIDE. 
PH 3 . 
Tin and zinc phosphides are prepared by adding the 
equivalent quantity of amorphous phosphorus to the re- 
spective metals in the molten state covered with ammo- 
nium carbonate. Iron phosphide, FeP, by heating finely 
divided iron and amorphous phosphorus together, copper 
phosphide, by heating copper filings with amorphous phos- 
phorus ; magnesium phosphide, by adding the equivalent 
quantity of amorphous phosphorus to melted magnesium ; 
sodium phosphide by carefully adding yellow phosphorus 



* By H. Moissan, Bull. Soc. Chim. [3], 4, 260. 



134 LABORATORY MANUAL OF 

to fused sodium under petroleum. The phosphides of tin, 
zinc, iron, and copper are not decomposed by water ; 
whilst those of sodium and magnesium, like that of calcium 
are decomposed by water. From magnesium phosphide, 
whether decomposed by water or by dilute hydrochloric 
acid, non-spontaneously inflammable hydrogen phosphide 
is obtained. From sodium phosphide, spontaneously in- 
flammable hydrogen phosphide is obtained, which, in a 
great measure, readily changes to solid phosphide. The 
phosphides of tin and zinc are decomposed by cold dilute 
hydrochloric or sulphuric acid, but those of iron and cop- 
per are but slightly attacked even on boiling. 

For the preparation of hydrogen phosphide from the 
phosphides of tin, zinc or magnesium, an Erlenmeyer flask 
of 200 to 300 c. c. capacity is fitted with a stopper carrying 
three tubes, one of which conducts carbonic anhydride gas to 
the bottom of the flask to displace the air, the second ad- 
mits the dilute acid from a tap-funnel, the third is the 
delivery tube. To the latter is attached a tube, filled with 
glass wool, from which the gas passes out into nitric acid 
in a dish. In the case of tin phosphide the flask is warmed 
gently on the water-bath at the commencement, after which 
the reaction proceeds regularly for thirty minutes to one 
hour, when as the reaction becomes slower, the flask may 
again be warmed. In the case of zinc or magnesium phos- 
phides, no external heating is requisite. The method is 
preferable to the preparation with potassium hydroxide and 
phosphorus or to that with calcium phosphide, and demon- 
strates the formation of the phosphide of hydrogen in 
analogous manner to the other compounds of hydrogen 
with the non-metals, ammonia excepted. The preparation 



INORGANIC PREPARATIONS. 1 35 

of zinc phosphide is also especially recommended as being 
simple. The synthesis of hydrogen phosphide may be 
shown by putting sodium phosphite or hypophosphite into 
a hydrogen generator, when the phosphide is readily de- 
tected in the gas evolved.* 



ARSENIC ACID. 
H 3 As0 4 . 

The arsenic acid liquid produced in preparing nitrogen 
tetraoxide (page 21) is poured off from the unchanged pieces 
of white arsenic, evaporated to dryness in a porcelain dish, 
and the residue again dissolved by heating with a little 
water. The solution must be free from arsenious acid, or 
else must be again evaporated, adding a little H 3 S04, and 
dissolved once more. If the solution is pure it is boiled 
down to a syrup, and left to crystallize at a low tempera- 
ture in a closed vessel, adding, if necessary, a small crystal 
of arsenic acid. When the concentration is perfect, very 
nice, large, compact glossy crystals will be obtained ; if the 
crystallization has occurred too quickly, the mass is dis- 
solved, the crystals are melted at a moderate heat, and 
then allowed to slowly crystallize, so that larger crystals 
may be obtained. 

Arsenic acid should dissolve readily in water, and 
with ferrous sulphate give no nitric acid reaction. The 
well-diluted solution mixed with a drop of HC1 should 
at first remain clear; when mixed with an equal volume 



* By R. Luepke, Chem. Centr., 1890, i i, 642 ; from Zeit. f. physikal. 
und chem. Unterricht, 3, 280. 



136 LABORATORY MANUAL OF 

of sulphureted hydrogen water should only become tur- 
bid upon standing some time. A solution of the acid 
in fuming HO should immediately give a thick yellow- 
precipitate with hydrogen sulphide. 

2HN0 3 + As 3 3 -f 2H 2 = N 2 3 4- 2H 3 As0 4 . Arsenic 
acid is not precipitated from aqueous solution by hydrogen 
sulphide, but from cone, hydrochloric acid solution ; it is 
at once precipitated, when a mixture of arsenic pentasul- 
phide, sulphur and arsenic trisulphide is thrown down. In 
such z. solution arsenic pentachloride, which is unknown in 
a pure condition, seems to be present, and this is decom- 
posed by hydrogen sulphide according to the equations : 

2AsCl 5 + 5H 2 S = As 2 S 5 + 10HC1; 

AsCl 5 + H 2 S = AsCl 3 + S + 2HC1; 

2AsCl 3 + 3H 3 S = AsgSg + 6HC1. 



HYDROGEN ARSENIDE. 

H As. 
The action of zinc on an acid solution of arsenious acid 
produces a gas containing 70 per cent, by volume of hy- 
drogen arsenide. Sodium amalgam containing not more 
than 4 grams of sodium in 50 c. c. of mercury, by its action 
on a concentrated solution of arsenious acid, produces a 
gas containing 86 per cent, by volume of hydrogen arsenide. 
A gas containing a large quantity of arsenic may be pre- 
pared by the action of aluminium on a somewhat dilute 
alkaline solution of potassium arsenite, while a solution of 
arsenic disulphide in potash, when subjected to the action 
of aluminium, evolves a gas quite free from arsenic* 

* A. Kavazzi, Rend. Ace. Bologna, 1886-7, 85. 



INORGANIC PREPARATIONS. 137 



ARSENIC PENTASULPHIDE. 
As 2 S 5 . 
When a solution of an alkaline arsenate, strongly acidi- 
fied with hydrochloric acid and saturated with hydrogen 
sulphide is heated in a closed vessel at ioo° C. for one 
hour the arsenate is completely converted into pentasul- 
phide. It contains no trisulphide, atffcl if due precau- 
tions have been taken to exclude air, no free sulphur. 
Pure arsenic pentasulphide is lemon yellow in color, 
does not yield any sulphur to carbon disulphide, and 
dissolves in ammonia without separation of sulphur. 
When the ammoniacal solution is agitated with silver nitrate 
and filtered a clear nitrate is obtained, from which nitric 
acid precipitates silver arsenate. Arsenical pyrates may 
be used instead of alkaline arsenate, in which case the 
finely pulverized ore is digested for some time in aqua 
regia until decomposed ; the chlorine is boiled out and hy- 
drogen sulphide passed through the cold solution as long 
as a precipitate forms ; this serves to remove heavy 
metals, as sulphides ; filter and wash with hydrogen sul- 
phide water, saturate with hydrogen sulphide, and pro- 
ceed as before.* 



ANTIMONY TRICHLORIDE. 

SbCl 3 . 
IOO grams powdered stibnite are heated with 500 c. c. 
crude HC1 in a flask, gradually adding about 4 grams po- 
tassium chloride. When the ore has disappeared filter off 

* L. W. McKay, Chem. News, 54, 287. 



138 LABORATORY MANUAL OF 

from the sulphur through glasswool, and distill out of the 
retort ; at first aqueous hydrochloric acid comes over, then 
a concentrated antimony chloride solution, which is fre- 
quently of a yellow color from iron chloride, finally nice 
white, pure antimony chloride, cooling in crystals, will pass 
over. Each of these products are caught up separately. 
The pure antimony chloride is refined in a test tube or 
small flask, the antimony chloride solution decomposed by 
a large quantity of water, whereby antimony oxychloride 
is precipitated as a fine white powder (Algaroth). 

The change Sb 3 S 3 + 6HC1 = 2SbCl 3 -f 3H 3 S which at 
first goes on energetically, but gradually becomes very 
slow, and may be hastened to a conclusion by adding the 
means of oxydation. 

The antimony chloride should melt at 73 ° C, boil at 
223 C, and crystallize from carbon disulphide in rhombic, 
glossy crystals. 



ANTIMONY OXYCHLORIDE. 

Sb40 5 Cl 2 . 

60 grams powdered antimony sulphide are thoroughly 
mixed in a mortar with 140 grams mercuric chloride, and 
slowly distilled from a gas retort over the gas stove at 
gentle heat. A flask is used as receiver, the neck of which 
has been broken off; the neck of the retort is heated at in- 
tervals with a Bunsen burner, to melt the antimony chlo- 
ride that solidifies in it. The distillate is dissolved in a 
little warm HC1, and then poured into a large quantity of 



INORGANIC PREPARATIONS. 1 39 

hot water ; the precipitate is washed by decantation and 

then dried. 

Sb 3 S 3 -f 3HgCl 3 = 2SbC] 3 + 3H g S, 
4SbC1 3 + 5H 2 = Sb 4 5 Cl 3 + 10HC1. 

The white crystalline powder should be insoluble in 
water, alcohol and ether, but soluble in carbon disulphide 
and chloroform. On heating it should give a sublimate 
of antimonious chloride, leaving behind antimony mon- 
oxide.* 

ANTIMONIOUS SULPHATE. 

Sb 2 (S0 4 ) 3 . 
20 grams finely powdered antimony are added to 400 
grams of boiling, distilled H 2 S0 4 and boiled in a platinum 
dish until the metal has disappeared. A part of the sul- 
phate crystallizes out of the hot solution, the rest upon the 
cooling of the liquid, in the form of small white needles. It 
is filtered through a platinum cone and dried on an earthen 
plate. 

BISMUTH NITRATE. 
Bi(N0 3 ) 3 + 5H 2 0. 

BASIC BISMUTH NITRATE. 
BiON0 3 + BiOOH. 

BISMUTH HYDROXIDE. 
B O OH. 

100 grams commercial bismuth and 50 grams sodium 
nitrate are heated in a nickel dish at faint red-heat. After 



* G. E. Stahl, Zufallige Gedanken und niitzliche Bedanken liber den 
Streit von den sogennaten sulfure Halle, 171 5, S. 346. 



I4O LABORATORY MANUAL OF 

the metal is completely oxydized boil thoroughly with 250 
c. c. water, adding a solution of 20 grams sodium hydrate 
in 150 c. c. water. The bismuth oxide filtered on the 
bare platinum cone is dissolved hot in a flask containing 
a mixture of 140 c. c. cone. HNO^ with 200 c. c. water, fil- 
tered through an asbestos filter and evaporated to crystal- 
lization. The mother liquid is evaporated further, and 
poured into ]/ 2 litre boiling water, whereupon the basic bis- 
muth nitrate separates in the form of a heavy white powder, 
which, after decanting, is collected on the filter and dried 
in the cold ; or else the acid solutions are precipitated 
with ammonia, the bismuth oxyhydrate decanted and pre- 
served as a paste. 

The impurities of commercial bismuth consist chiefly 
of arsenic and antimony, the oxides of which go into 
solution upon boiling with soda. 

The bismuth value of the crystallized nitrate should 
be ascertained from a weighed sample by converting it 
into bismuth oxide in a covered porcelain crucible, heat- 
ing at first carefully, then energetically. Further, a sample 
is dissolved in very dilute nitric acid, the solution poured 
into an excess of hot soda, and the filtrate tested for arsenic 
and antimony. 



BISMUTH IODIDE. 
Bil 3 . 
20 grams iodine are mixed with 35 grams finely pow- 
dered bismuth in a mortar, quickly poured into a retort, 
and slowly heated on the gas stove. When the reaction 
is finished the small quantity of surplus iodine is driven out 



INORGANIC PREPARATIONS. I4I 

by a current of dry carbonic acid gas, and the temperature 
raised until the bismuth iodide sublimes in form of very 
large crystals, similar in appearance to iodine. 

Boiling water should convert the powdered bismuth 
iodide into red oxyiodide. 



BISMUTH OXYIODIDE. 
BiOI. 

95.4 grams powdered crystallized bismuth nitrate 
(page 139) are dissolved in 120 to 160 c c. glacial acetic 
acid by warming gently. At the same time 33.2 grams 
potassium iodide and 50 grams crystallized sodium acetate 
arc dissolved in 2 litres cold water. The second solution 
is placed in a dish and the first added to it in a very thin 
stream from a dropping funnel, with frequent stirring. At 
the point where the liquid strikes a greenish-black pre- 
cipitate forms at first ; upon stirring this immediately 
changes to a lemon color. On further addition of the 
bismuth solution the product assumes a dark, brick-red 
color. The precipitate settles very readily. It is decanted, 
filtered and dried at ioo° C. 

Bi(N0 3 ) 3 + 3Kt = B1I3 + 3KN0 3 ; . 
Bils-f; H 3 Q = BiOI t 2HI. 

The hydriodic acid reacts with the sodium acetate, 
and the potassium iodide formed again takes part in the 
reaction. 

Heated in a dry test-tube the compound should yield 
violet iodine-vapors, and leave behind bismuth oxide ; on 
shaking with water no halogen acid should be set free, 



142 LABORATORY MANUAL OF 

and it should be free from arsenic and bismuth subnitrate : 
0.2 gram shaken with 2 grams dilute sulphuric acid 
should give a filtrate which, when mixed with twice its 
volume of cone. H 2 S0 4 , should be permanently colored blue 
by a drop of indigo solution (discoloration nitric acid).* 



BISMUTHIC ACID. 
HBi0 3 . 

20 grams of bismuth bromide and 40 grams of potas- 
sium bromide are dissolved in 60 grams of water and 
mixed with excess of bromine. The solution is then 
poured drop by drop into an almost boiling solution of I OO 
grams of potassium hydroxide in 150 grams of water, the 
alkali remaining in excess at the end of the reaction. A 
very dense red-brown precipitate forms immediately. This 
is washed repeatedly with boiling water by decantation, 
and, after a long time, part of the product forms a brown 
emulsion with the water, whilst a red-brown compound 
remains at the bottom of the vessel. The emulsion is de- 
canted off, and can be precipitated by addition of a few 
drops of nitric acid. The non-emulsified product is 
washed with hot water until no longer alkaline, and one 
portion is washed for several days longer. Both portions, 
when dried at ioo° C, have the composition 4KBi03, 
3HBi0 3 . The same product is obtained from bismuth 
chloride ; it dissolves easily in hydrochloric acid, with 
evolution of chlorine, but is soluble only with difficulty in 
warm nitric acid. When heated it becomes pale-yellow, 



* B. Fischer, Die neueren Arzeneimittel, III. Aufl., s. 20. 



INORGANIC PREPARATIONS. 143 

loses oxygen, then becomes brown, melts, and on cooling 
is pale-yellow. 

Prolonged washing with boiling water yields a product 
which, after being dried at 100 C, has the composition 
KBi0 3 ,HBi0 3 . 

All these products when treated with warm, dilute 
nitric acid lose the whole of their potassium, and yield 
brick -red bismuthic acid, HBiOs. Very often the residue 
dried at 100 C. has the composition rIBi0 3 ,Bi 2 .* 



ANTIMONY AND BISMUTH SULPHATES. 

Anhydrous antimony sulphate, Sb 2 (S0 4 ) 3 , is best pre- 
pared by dissolving the trisulphide in concentrated sul- 
phuric acid heated to the temperature at which it com- 
mences to vaporize ; the salt is deposited as a fine, very 
deliquescent, white crystallized powder. Its products of 
decomposition with water vary with the conditions, such 
as mass and temperature ; with boiling water the salt is 
completely decomposed into antimonious oxide (contain- 
ing less than 1 per cent, of water) and sulphuric acid, whilst 
with water at ordinary temperatures a basic sulphate, 
5SB 2 3 2S0 3 7H 2 0, is produced. The sulphate is almost 
completely converted into antimonious chloride by a cur- 
rent of hydrogen chloride. Anhydrous bismuth sul- 
phate, Bi 2 (S0 4 ) 3 , prepared in a manner similar to the 
antimony salt, crystallizes in very hygroscopic, glis- 
tening needles ; when evaporated with water it yields a 



G. Andre. Compt. Rend., 113, S60-862. 



144 LABORATORY MANUAL OF 

slightly coherent powder of the composition BiglSO^ + 
3H 2 0, but on heating it with water at the ordinary tem- 
perature, and evaporating the solution, a powder of the 
composition 2Bi 2 (S0 4 ) 3 + 7H 2 is obtained ; lastly, if the 
salt be frequently treated with water, the final product is 
a hydrate, Bi 2 ,0 3 ,S0 3 ,H 2 0. It is probable that under 
favorable conditions the sulphate is converted by hydro- 
chloric acid into bismuth trichloride.* 



COBALT NITRATE. 

Co(N0 3 ) 2 , Crystallized -j- 5H 2 0. 
Fuse in a Hessian crucible 3 parts of potassium disul- 
phate, and add to the fused mass, in small portions at a 
time, 1 part of well-roasted cobalt ore (the purest zaffre 
you can procure) reduced to fine powder. The mass 
thickens and acquires a pasty consistency. Heat now 
more strongly until it has become more fluid again, and 
continue to apply heat until the excess of sulphuric acid is 
completely expelled, and the mass accordingly no longer 
emits white fumes. Remove the fused mass from the 
crucible with an iron spoon or spatula ; let it cool and 
reduce it to powder; boil this with water until the undis- 
solved portion presents a soft mass ; then filter the rose- 
red solution, which is free from arsenic and nickel and 
mostly also from iron. Add to the filtrate a small quantity 
of sodium carbonate, so as to throw down a little cobalt 
carbonate ; boil and filter. Precipitate the solution, which 
is now free from iron, boiling with sodium carbonate; wash 
the precipitate well, and treat it still moist with oxalic 



* C. Hensgen, Rec. Trav. Chim., 4, 401-413. 



INORGANIC PREPARATIONS. 1 45 

acid in excess. Wash the rose-red cobalt oxalate thor- 
oughly, dry and heat to redness in a glass tube, in a cur- 
rent of hydrogen gas. This decomposes the oxalate into 
carbonic acid gas, which escapes, and metallic cobalt, which 
is left behind. Wash the metal first with water containing 
acetic acid, then with pure water ; dissolve in dilute nitric 
acid, treat, if necessary, with hydrogen sulphide, filter the 
fluid from the copper sulphide, etc., which may precipitate, 
evaporate the solution in the water-bath to dryness. 

Solution of cobalt nitrate must be free from other 
metals, and especially from salts of the alkali metals ; 
when precipitated with ammonium sulphide and filtered, 
the filtrate must, upon evaporation on platinum, leave no 
fixed residue. 



HYDROGEN PEROXIDE. 
H 2 3 . 
One-half litre commercial hydrogen peroxide is cooled 
in a flask to o° C. and mixed with a cold, saturated barium 
hydrate solution until a permanent precipitate forms, and the 
solution has become alkaline. The filtered solution, cooled 
and shaken, is allowed to flow into 2 litres of ice-cold 
barium hydrate solution. When the crystalline precipitate 
no longer forms, the peroxide is filtered and rinsed with a 
little ice-water. Now 20 c. c. cone. H 2 S04 are mixed with 200 
c. c. water, the solution carefully cooled in a freezing mix- 
ture of ice and common salt, and enough of the still moist 
barium peroxide added, shaking, until the solution reacts 
only faintly acid. Then it is allowed to settle ; the ice- 
cold solution is filtered and neutralized with a few drops 



I46 LABORATORY MANUAL OF 

of dilute barium hydrate, until neither H 3 S0 4 nor barium 
remains in the solution. Then the turbid solution is fil- 
tered, and a part of the thus obtained pure hydrogen per- 
oxide solution evaporated on a porcelain plate in vacuum 
over H 3 S0 4 . 

The reactions: H 3 3 + Ba(OH) 3 = Ba(OH) 4 and 
Ba(OH) 4 + H 3 S0 4 = BaS0 4 + H 3 3 will only take place in 
the cold and in not too high concentration. If these con- 
ditions are not fulfilled, oxygen developes richly, and the 
gain will prove a minimum. 

The anhydrous peroxide should be a syrupy, bitter- 
tasting solution of 1.46 sp. gr., which on warming decom- 
poses readily. The watery solution should also have the 
peculiar characteristic taste ; and yield, when mixed with 
dil. sulphuric acid, ether and a drop of dilute potassium 
dichromate solution, an intense blue, ether-soluble color; 
be free from HC1,H 3 S0 4 and barium. One per cent, of 
alcohol is added for preservation. 

The value is determined by decomposing 1 c. c. hydro 
gen peroxide solution with excess of permanganate of potas- 
sium and dil. H 3 S0 4 in a nitrometer, or else by titration 
of 5 c. c. with j^ normal permanganate in sulphuric acid 
solution. * 

Another method for the preparation of pure hydrogen 
peroxide is to take the solution of hydrogen peroxide 
which results from the action of hydrochloric acid (sp. gr. 
1.1) on barium dioxide, and is extracted by shaking with 
ether; the ethereal solution is agitated with distilled water, to 
which it yields the dissolved hydrogen peroxide. By repe- 
titions of this process, a pure, neutral solution correspond- 

* J. Thomsen, Ber. 7-74. 



INORGANIC PREPARATIONS. I47 

ing with 0.8 to 0.9 per cent, of hydrogen peroxide is obtain- 
able, from which the dissolved ether may be eliminated by 
distillation under reduced pressure.* 

It can also be prepared by adding sodium carbonate 
to the commercial 3 per cent, aqueous solution of hydro- 
gen peroxide, until the reaction is distinctly alkaline. The 
solution is then filtered, and shaken up for 3 to 5 minutes 
with 10 to 12 times its volume of e£her, which extracts 
about half of the hydrogen peroxide originally present, 
and leaves behind most of the impurities. The ethereal 
layer is separated and reduced to o.Oi to 0.0025 of its 
original volume on the water-bath. The remainder of 
ether is removed in a bell jar by solid paraffin. The loss 
of hydrogen peroxide during the evaporation of the ether 
is only 7 to 10 per cent. 

Operating in this way two solutions are obtained : (a) 
sl colorless solution with distinctly acid reaction, and sp. gr. 
1. 1756, which contains 54 grams of anhydrous hydro- 
gen peroxide in 100 c. c; (b) a thick transparent 
slightly yellow, acid liquid, of sp. gr. 1.2475, which con- 
tains 79.6 grams of hydrogen peroxide in 100 c. c.f 

Hydrogen peroxide chemically pure can be prepared 
by mixing hydrogen peroxide of commerce with 0.25 per 
cent, of phosphoric acid and then while vigorously stirring, 
barium hydroxide is added until the solution is neutral to 
litmus. The clear solution is poured into a cold saturated 
solution of barium hydroxide and the precipitate of barium 
dioxide is well washed and may be kept for the prepara- 
tion of pure hydrogen dioxide. For this purpose it is 



* L. Crismer. Bull. Soc, Chim. [3], 6, 24-25. 
\ P. Shiloff, J. Russ. Chem. Soc, 25, 293. 



148 LABORATORY MANUAL OF 

made into a thin magma and carefully decomposed by 
dropping steadily into dilute sulphuric acid containing 12 
per cent, of concentrated acid ; and excess of sulphuric 
acid being removed by hydroxide and vice versa. Excess 
of barium dioxide must be avoided, as it decomposes hy- 
drogen dioxide.* 

POTASSIUM AND SODIUM PEROXIDES. 

When potassium is dropped into molten potassium ni- 
trate the metal burns with a bright light, with the forma- 
tion of yellowish potassium peroxide which dissolves in the 
fused mass, imparting to it a deep, rich red color. In a 
similar manner sodium and sodium nitrate give rise to a 
yellowish-red solution, whilst potassium and potassium 
nitrate give a brown-red solution. In all cases the color 
disappears on cooling, but on heating again reappears. The 
aqueous solutions from the colorless masses give a greenish 
precipitate with copper sulphate. The action of sodium 
on fused potassium chlorate is attended with dangerously 
explosive violence. f 

SULPHUR MONOCHLORIDE, 

S 2 C1 2 , 

AND 

SULPHUR DICHLORIDE, 

sci 2 . 

300 grams sulphur are heated to its melting point in a 
tubulated retort over a low flame, and as in the case of tinte- 



* Mann. Chem. Zeit., 12, 857. 

f H. C. Bolton Chem. News, 53, 289-290. 



INORGANIC PREPARATIONS. I49 

trachloride a rapid stream of dry chlorine gas is passed 
close to the surface of the melted sulphur. The vola- 
tile chloride is redistilled in a side neck flask, and a 
little dissolved sulphur remains as a residue. 67.5 grams 
of the sulphur monochloride are cooled to o Q C. and 
saturated with dry chlorine gas. The sulphur dichloride 
so produced must weigh 103 grams. It is preserved in 
well-stoppered bottles. 

In the redistillation of the chloride of sulphur the 
higher chlorides change into sulphur monochloride; on the 
other hand at 0° C. sulphur monochloride combines with 
another molecule of chlorine : S 2 C1 2 + Cl 2 = 2SC1 2 . 

The sulphur monochloride should form a yellowish-red, 
strong-smelling solution of 1.7 sp. gr., and the sulphur 
dichloride a dark red solution, which should develop 
chlorine at ordinary temperature the quantity increasing 
with the temperature. 



PREPARATION OF CHROMIUM FROM POTAS- 
SIUM CHROMIUM CHLORIDE AND 
MAGNESIUM. 

Chromium can be quickly prepared in an almost chem- 
ically pure condition in the following manner : Potassium 
dichromate (100 grams) is dissolved in the least possible 
quantity of water, the solution mixed with hydrochloric 
acid of sp. gr. 1.124 (400 c. a), and then 80 per cent, al- 
cohol (100 c. c.) gradually added. The solution of potas- 
sium chromium chloride obtained in this way is treated with 
potassium chloride (160 grams), the filtered solution evap- 



150 LABORATORY MANUAL OF 

orated to dryness, the residue heated until anhydrous, freed 
from the green portions, which are produced by the de- 
composition of the double salt, then powdered, and mixed 
with magnesium filings (50 grams). This mixture is heated, 
for about half an hour, to a bright red heat, in a closed 
Hessian crucible in a blast-furnace, care being taken that 
the potassium chloride does not volatilize completely, 
otherwise the chromium is partially oxidized. The melt is 
separated from the superficial layer of chromium oxide, 
treated with water, and the finely divided metal freed from 
salts and unchanged magnesium by washing it with water ; 
then boiling it with dilute nitric acid, and again washing 
with water, all the washing being done by decantation. 
The yield of the metal, dried at iOO° C, is about 27 grams. 
Chromium, prepared in this way, is a light-gray, crys 
talline, non-magnetic powder of sp. gr. 6.7284 at 16° C. 
it can be melted in a Deville's furnace, but only with great 
difficulty, and after being melted it shows a silvery fracture. 
Two analyses of the powder showed that it contained 
99.53 to 99.57 per cent of chromium, and that it was free 
from silver and magnesium.* 



CHROMYL CHLORIDE. 

Cr0 3 Cl 2 . 

200 grams neutral potassium chromate and 122 grams 
common salt are melted in a Hessian crucible at a moder- 
ate temperature, the fusion is poured on a piece of sheet- 



* E. Glatzel, Ber. 23, 3127-3130. 



INORGANIC PREPARATIONS. I 5 I 

iron and broken in coarse pieces, these are digested with a 
mixture of 66 c. c. fuming HgSO^ (1.096 sp. gr.) and 134 
c. c. ordinary cone. H0SO4 in a roomy retort with con- 
denser. The reaction is very violent at first ; when it mod- 
erates, the retort is heated until no more brown drops 
pass over, and the distillate is rectified in a fractional dis- 
tilling flask. The chromyl chloride is preserved in sealed 
tubes. 

Cr0 3 + 2HC1— H 2 = Cr0 3 Cl 2 . 

The dark red oxychloride which fumes when exposed 
to the air should boil at 1 16 C. 



ANHYDROUS CHROMIUM CHLORIDE. 

CrCl 3 . 

The chromium oxide obtained as per directions on 
page 151, while still moist, is kneaded to a paste with 50 
grams powdered coal and thick starch paste. Of this, bars 
are formed which are cut in pieces of 2 to 3 cm. long. The 
pieces, dried at a moderate heat, are packed with coal 
powder in a Hessian crucible, covered with a layer of coal 
powder, closed with an iron cover and ignited for 15 
minutes in Roessler's furnace. Now a porcelain tube is 
set upright in a Hessian crucible, the crucible filled with 
the pieces of chromium oxide mixture which have been 
cooled and separated from the surplus coal-powder, a sec- 
ond crucible of the same size with perforated bottom is 
placed upon it bottom up. A short glass tube passes 
through a small hole bored in the side of the upper cruci- 



152 



LABORATORY MANUAL OF 



ble. The tubes are wound with a little asbestos cord and 
fit tight in the openings ; in order to make both crucibles 
tight, a narrow, thin strip of soft asbestos board is wrapped 
around the joint and carefully wound with 
asbestos cord, finally the asbestos cord is 
saturated with water glass and dried at 
moderate heat (See fig. 10.) Then the 
crucibles are placed in a Roessler's anneal- 
ing furnace and this covered with two 
semicircular pieces of thick sheet-iron 
which have an opening in the center 
through which the upper crucible appears. 
It is first heated in a current of carbonic 
acid until no trace of moisture is shown 
on the glass tube. Then the strongest 
heat is applied and it is ignited in a cur- 
rent of chlorine, the uncombined chlorine 
passes out through the glass tube and is 
absorbed in soda. 

Upon cooling the chromium chloride is found sublimed 
in the upper crucible in violet-red very glossy scales which 
are insoluble in water. 

Cr 3 3 + 3C + 6C1 = 2CrCl 3 + 3CO. 




Fig. 10. 



CHROMIUM OXIDE. 
Cr 3 3 . 

250 grams potassium dichromate are thoroughly mixed 
with 50gramsof sulphurplaced in a clay crucible covered and 



INORGANIC PREPARATIONS. I 53 

ignited for one hour in Roessler's annealing furnace. The 
green contents of the crucible are ground, boiled several 
times with water, filtered and dried. 

K 3 Cr 3 O r + S = K 2 S0 4 + Cr 2 3 . 

Only traces of the green powder should go into solu- 
tion on boiling it with dilute hydrochloric acid. 



CHROMIUM ACETATE. . 

(CH 3 COO) 3 Cr. 

500 grams fuming HC1 are poured over 1 00 grams po- 
tassium dichromate in a flask, and the chlorine gas, which 
develops, upon warming, after being washed with water, is 
used in the preparation of chlorine water or of hypo- 
chlorite of sodium. The remaining solution is evaporated 
to a very small volume, poured off from the separated po- 
tassium chloride into a flask with 300 grams of granulated 
zinc and rinsed with 400 c. c. fuming HC1. The flask, in 
which a violent evolution of hydrogen should take place, 
is closed with a double-bored rubber stopper similar to 
that of a wash bottle. As soon as the solution has as- 
sumed a light blue color similar to copper sulphate solution, 
the glass tube permitting the free passage of the gas is 
closed, so that the hydrogen which continues to develop 
vigorously presses the solution out of the flask through 
the second tube which reaches to the bottom. It is filtered 
through a small bulb-tube with asbestos and then enters 



154 LABORATORY MANUAL OF 

directly, without coming in contact with air, into a solu- 
tion of 500 grams crystallized sodium acetate in 2 litres of 
water. The red precipitate is washed by decantation sev- 
eral times with water saturated with carbonic acid and pre- 
served as a paste.* 

K 3 Cr 2 7 + 14HC1 = 2KC1 -f 2CrCl 3 + 6C1 + 7H 2 ; 

2CrCl 3 + Zn = 2CrCl 3 + ZnCl 2 ; 

CrCl 2 + 2CH 3 COONa = 2NaCl + CH*— COO> Cn 

The reduction of the chromium chloride only takes place 
rapidly and completely in concentrated hydrochloric acid 
solution with large excess of zinc. Chromium monochloride 
absorbs the oxygen of the air with great rapidity, while the 
insoluble chromium acetate is fairly stable in air. 

The red paste should form a blue solution with diluted 
HC1, and by energetic absorption of oxygen this quickly 
turns dark green. 



POTASSIUM CHLOROCHROMATE, 

CrO, < £j K 

IOO grams potassium dichromate r r e powdered and 
gently heated in a flask with a mixture of 100 c. c. of 
water and 130 grams pure fuming HC1. As soon as dis- 
solved, it is filtered and allowed to settle. Next day the 



* Pfordten Annalen, 228, 113. 



INORGANIC PREPARATIONS. I 55 

crystals are separated from the mother liquor by decanta- 
tion and dried on an earthen plate. 

KO— C1O2 -> n , 9Rri _ KO— Cr0 2 Cl_^TT n 
KO— CO, -^ ° + 2HC1 - KO— Ci 0X1 ' Hs °- 

The large, red prisms or plates develop chlorine gas on 
heating to ioo°C. 



SELENIUM. 

Se. 

Seleniferous material or residues are melted in a Hes- 
sian crucible with a mixture of equal parts soda and salt- 
petre. The cooled fusion is boiled up with water, the ex- 
tract condensed to small volume, and the solution, which 
has been made strongly acid with cone, hydrochloric acid, 
is boiled with a reversed condenser until no more chlo- 
rine gas escapes. Now it is diluted in a large flask with 
plenty of hot water, and commercial sodium disulphite 
dropped into the boiling liquid as long as a red, very vol- 
uminous precipitate, which quickly clots to blackish, ugly 
masses, is formed. The separated selenium is settled, col- 
lected on a filter and dried. 

In fusing with soda and saltpetre seleniferous mate- 
rials produce selenates ; selenic acid is quickly reduced 
in cone, solution by muriatic acid : 

H 2 Se0 4 f -2HC1 = H 3 Se0 3 + 2C1 + H 2 0. 
Selenious acid is decomposed by sulphurous acid : 
H 2 Se0 3 + 2H 2 S0 3 = Se + 2H 2 S0 4 + H 2 0. 

The selenium should melt at 217 C, and when cooled 
slowly crystallize in dark-gray, metallic-shining masses ; 



156 LABORATORY MANUAL OF 

it should dissolve in cone, sulphuric acid, with a green 
color, and be reprecipitated out of this solution by water 
as a very voluminous red armorphous deposit. Heated 
in the air it should burn to selenium dioxide without re- 
sidue, leaving an odor of radishes. 



HYDROFLUOSILICIC ACID. 

H 3 SiF 6 . 

IOO grams calcium fluoride powder are mixed with 
100 grams dry quartz-sand (sea-sand), and carefully heated 
with 350 c. c. cone, sulphuric acid. The escaping gas is 
led through an empty bottle containing a safety-tube 
closed with a little cone, sulphuric acid, and then into a 
porcelain dish, at the bottom of which a small vessel with 
mercury has been placed. The gas tube is fastened so 
that it dips into the mercury, and then 400 c. c. distilled 
water are poured over it. After the gas evolution has 
ceased, the silicic acid, which has separated in the water, 
is filtered, washed with a little water, until the combined 
filtrates amount to 400 c. c, and the still cloudy acid is 
filtered through a folded filter. 

By the water-absorbing action of the sulphuric acid 
there is a formation of silicon fluoride : Si0 3 + 4HF— 2H 3 
= SiF 4 ; this gas is decomposed by water : 3SiF 4 -f-4H 3 
= 2H 3 SiF 6 +Si(OH) 4 . 

The acid should yield a precipitate (Ba 3 Si0 4 ) with 
barium chloride, but not with strontium chloride, in hydro- 
chloric acid solution. To determine its value, the acid 
is titrated with soda solution to alkaline reaction. The 



INORGANIC PREPARATIONS. I 57 

neutralization of the acid on titration with soda corresponds 
with the equation : H 3 SiF 6 + 6NaOH = 6NaF 4- Si(OH) 4 f 
2H 2 0. 



PERCHLORIC ACID. 

HCIO4. 

50 grams potassium perchlorate are distilled out of a 
good-sized retort with a mixture of 100 grams cone. 
H2SO4 and 20 c. c. water. The distillate is freed from chlo- 
rine gas by gently warming, a few centigrammes of silver 
sulphate and barium carbonate added, the trifling precipi- 
tates of each filtered separately, and the filtrate redis- 
tilled. 

KCIO4 + H 2 S0 4 =, HCIO4 + HKSO4. 

The crude acid still contains traces of HC1 and H 3 S0 4 , 
which are removed in the manner described. 

In a solution of potassium chlorate a drop of the acid 
produces a thick crystalline precipitate. 



MANGANESE. 

Mn. 

300 grams crystallized manganous chloride are grad- 
ually dried in a porcelain dish on the gas stove, 
and the pieces which have formed, powdered in a hot 
mortar and dried until the pale pink-colored powder fails 
to clot and a sample heated in a test-tube shows no mois- 
ture. 75 grams of the anhydrous manganous chloride are 



158 LABORATORY MANUAL OF 

thoroughly mixed in a warm condition with 150 grams 
dry potassium chloride (the latter must first be heated 
in a nickel or iron dish until it no longer decrepitates), and 
the mixture packed tight in a clay crucible, 12 cm. high 
and 7 cm. wide. The crucible is covered and heated in 
the furnace. When the crucible has become red-hot and 
the contents are soft, 18 grams magnesium in sticks are 
thrown in, in pieces of from 3 to 4 grams each, closing the 
crucible immediately after adding each piece and waiting 
for the faint reaction. The real difficulty is in rapidly 
producing the exceedingly high temperature in the fur- 
nace required to fuse the manganese that has formed. 
This can be accomplished in Roessler's furnace by pro- 
viding a very good gas supply and by introducing a 
strong oxygen current through the air-openings on the side 
of the furnace. (The oxygen is generated directly from a 
large retort, with potassium chlorate and a little black 
oxide manganese, which is heated a few minutes before 
adding the magnesium. The air-openings of the furnace 
are closed loosely with strips of asbestos board, through 
which the gas-tubes conveying the oxygen pass.) But a 
well-built brick, air or blast furnace, with coke fire, is 
preferable. The severe heat must last no longer than 
half an hour. Upon cooling, if the operation has proved 
successful, the manganese will be found as a regulus. If, in 
place of this, only a fine black metallic powder be 
found which, on exposure to air, changes very readily 
into manganese dioxide, then the heat was too low. If, 
on the other hand, the metal has solidified in crusts and 
granules, which have not combined to a regulus, then the 
crucible contents are ground, the light particles quickly 



INORGANIC PREPARATIONS. I 59 

elutriated with a large quantity of water, then filtered, 
quickly washed with alcohol and ether, dried between fil- 
tered paper, and the metallic powder so obtained is pre- 
served in well-closed bottles. 

MnCl 2 + Mg = MgCl 2 + Mn. 
The magnesium chloride volatilizes and reacts with the 
water-vapor of the gases of combustion to form hydrogen 
chloride and magnesium oxide. During the operation 
there is a considerable evolution of hydrochloric acid gas. 

Manganese is a brittle, glossy metal, when exposed to 
the air, especially in a finely divided and moist condition, is 
very easily oxidizable and when excess of diluted HC1 is 
poured over a sample, the metal should dissolve clearly 
with a vigorous evolution of hydrogen. The solution 
prepared hot should show no turbidity with excess of 
ammonia, or at most a hardly noticeable one. When am- 
monium sulphide is added to this ammoniacal solution, a 
precipitate of flesh- colored manganese sulphide forms, 
which gradually turns green on boiling. The filtrate from 
the manganese sulphide mixed with sodium phosphate 
gives a precipitate of magnesium phosphate which is never 
entirely absent, but in successful working should be very 
slight. 



MANGANESE CHLORIDE. 
MnCl 2 + 4H 2 0. 

Residues of chlorine produced from black oxide of man- 
ganese and HC1 are evaporated to dryness in a porcelain 
dish, and the residue heated for a time on the gas stove 
with low flame. It is then boiled up with water and Ttrth 



160 LABORATORY MANUAL OF 

of the filtrate precipitated with excess of soda solution. 
The precipitate is washed with water decanting several 
times, then the main quantity is added to the solution and 
digested with it, warming until a filtered sample, mixed 
with ammonium sulphide, shows a pure flesh-colored pre- 
cipitate, which on dissolving in dil. acetic acid leaves no 
residue. It is then filtered and evaporated to crystalliza- 
tion. 

On heating the dry chlorides and boiling with water, 
the compounds of the trivalent metals (iron, aluminium) 
decompose with formation of insoluble basic salts. Pos- 
sibly the rest of the compound is precipitated by the 
manganese carbonate 
3MnC0 3 + Fe 3 Cl 6 + 3H 2 = 3MnCl 3 + Fe 3 (OH) 6 + 3C0 3 . 

The magnanese chloride is tested for the absence of 
iron, barium, calcium and magnesium salts. 



SOLUBLE MANGANESE OXIDE. 

4(Mn0 3 H 3 0),Mn 3 4 . 

Obtained by acting on potassium permanganate with 
sodium thiosulphate, and thoroughly washing the precipi- 
tate with water. As soon as all the potassium has been 
removed, a brown solution is obtained, from which the oxide 
is precipitated on the addition of any salt. The manga- 
nese solution can be kept for a long time in sealed tubes, 
but if filtered through paper the manganese is completely 
precipitated.* 



* W. Spring and G. de Boeck, Bull. Soc. Chim., 48, 170. 



INORGANIC PREPARATIONS. l6l 



MANGA NOUS SULPHIDE. 
MnS. 

Manganous sulphide is thrown down from ammoniacal 
manganous solutions by ammonium sulphide as a pink 
precipitate, which the older workers supposed to be a hy- 
drated sulphide ; however, it is shown that if it is collected, 
washed in an atmosphere of hydrogen sulphide, and dried 
at jo° C. in a current of carbonic anhydride it has the 
composition MnS. The sulphide thus obtained consists 
of tiny, reddish, transparent crystals, and is contaminated 
with a little sulphur, which may be extracted by treat- 
ment with carbon bisulphide ; its sp. gr. at \J Q C. is 3.55. 

If the red precipitate be well washed, and left in a 
solution of ammonium sulphide for a few days, it turns 
green ; the same change is also brought about by heating 
the red powder at 300 to 320 C. The green modifica- 
tion is crystalline, and has the same composition as the 
red, but a somewhat higher sp. gr., namely, 3.63, re- 
ferred to water at 17 C. Neither modification loses sul- 
phur on heating.* 



MANGANESE SULPHATE. 

MnS0 4 ,5H 2 0. 

A concentrated solution of MnS0 4 is treated with 95 
per cent, alcohol, when almost all of the sulphate sepa- 
rates out as a syrupy liquid, which after a short time 



By U. Anton v and P. Domnint, Gazzetta, 23, i., 560-567. 



162 LABORATORY MANUAL OF 

begins to form crystals. If, at this point, the liquid and 
alcohol be repeatedly and strongly shaken, a crystalline 
meal results, but if allowed to remain at rest, well-formed, 
reddish white, prismatic crystals are deposited.* 



POTASSIUM MANGANATE. 
K 2 Mn0 4 . 
Potassium hydroxide (2 mols) is placed in a crucible, 
some water is added, and finely divided potassium per- 
manganate (2 mols) is added, with constant stirring and 
heating. After two hours at a faint red heat the crucible 
is cooled, and the manganate placed in a well-stoppered 
flask, to prevent access of air and contact with organic 
matter, t 

BARIUM MANGANATE. 
BaMn0 4 . 
This green pigment is prepared by heating manganese 
carbonate with 2 to 2. 5 times its weight of commercial barium 
dioxide in a porcelain crucible. A better green is ob- 
tained when well-pulverized manganese dioxide (contain- 
ing 91 per cent, of Mn0 2 ) is heated with three times its 
weight of barium dioxide.f 



PREPARATION OF BARIUM PERMANGANATE. 

BaMn 3 8 . 
Potassium permanganate (100 grams) and barium ni- 
trate (140 grams) are disolved in water (iyi litres), and 

* B. Classen, Arch. Pharm. [3] 25, 310. 

f A. Joller, Rep. Anal. Chem. 1887, No. 33. 

% E. Donath, Dingl. Polyt. Jr. 263, 246. 



INORGANIC PREPARATIONS. 163 

to the boiling solution barium hydroxide is added in por- 
tions of 20 grams, until no further evolution of oxygen 
takes place. The whole is then warmed until the solu- 
tion has become colorless, the precipitate of barium man - 
ganate (containing also some peroxide and carbonate) is 
collected, washed 5 times by decantation with 5 litres of 
boiling water, collected on the filter-pump, washed 10 
times more with boiling water, suspended in water (1 litre) 
and carbonic anhydride, and superheated steam passed into 
the mixture for 10 hours. The solution is then filtered 
twice through an asbestos filter ; it contains 65 to 80 grams 
of barium permanganate.* 



FERRIC CHLORIDE. 

Fe 2 Cl 6 . 

Heat small iron nails in a flask with a mixture of 10 
parts of water and one part of pure hydrochloric acid until no 
further evolution of hydrogen is observed, even after add- 
ing the nails in excess; filter the solution into another flask, 
and conduct into it chlorine gas, with frequent shaking un- 
til the fluid no longer produces a blue precipitate in a solu- 
tion of potassium ferricyanide. Heat until the excess of 
chlorine is expelled. 

Solutions of ferric chloride must not contain an excess of 
acid ; this may be readily ascertained by stirring a diluted 
sample with a glass rod dipped in ammonia, when the 
absence of any excess of acid will be proved by the forma- 
tion of a precipitate which shaking the vessel or agitating 
the fluid fails to redissolve. Potassium ferricyanide must 
not impart a blue color to it. 

* By F. Muthmann, Ber. 26, 1016-1018. 



164 LABORATORY MANUAL OF 



ANHYDROUS FERROUS CHLORIDE. 

FeCl 2 . 
Into a retort, which has been warmed and fitted up for 
the production of ferric chloride, about 20 grams 
anhydrous ferric chloride are poured as quickly as 
possible. A strong current of carefully dried hydrogen 
gas, developed from a Kipp's apparatus, is passed over it 
The retort is placed on a gas stove which may be lighted, 
when it is certain that the air has been entirely removed from 
the apparatus; the heat should be moderate. A strong evo- 
lution of hydrogen chloride takes place at once ; the gas 
is collected in water. When the chloride in the retort has 
changed to a white crystalline mass and the evolution of 
HC1 ceases, the operation is concluded. It is then allowed 
to cool in a slow current of hydrogen ; the retort is broken 
while still warm and the collected chloride preserved in the 
same manner as the ferric chloride. 

Fe 2 Cl 6 + 2H = 2FeCl 2 + 2HC1. 

Anhydrous ferrous chloride forms in white scales, fairly 
stable when exposed to air, melting when heated vigorous- 
ly and subliming at a very high temperature. 



ANHYDROUS FERRIC CHLORIDE. 

Fe 2 Cl 6 . 
50 grams bright iron wire 1 mm. thick in pieces 6 to 8 
mm. long are placed in a tubulated glass retort of ^ litre 
capacity and strongly heated on the gas stove, a chlorine cur- 



INORGANIC PREPARATIONS. 165 

rent, dried by two wash bottles with sulphuric acid, is led 
into it through a glass tube, which passes through a cork in 
the tubulure of the retort ending just above the iron. The 
neck of the retort is closed with a bored cork; the es- 
caping chlorine gas is either led out through a rub- 
ber tube or else absorbed in flasks by soda or alcohol. 
After the operation has lasted 1 to 2 hours, the gas current 
and heat are interrupted, the chlorine which fills the re- 
tort is removed by dry carbonic acid, the retort broken 
while still hot over a large sheet of smooth paper, a • 
the ferric chloride separated from the broken glass and un- 
changed iron, from which it is very easily removed ; it is 
then rapidly placed in dry and warm test tubes prepared in 
readiness, tared and fitted with suitable stoppers which are 
immediately closed by heating before the blowpipe, taking 
care that the aqueous products of combustion do not enter 
the tubes. 

The ferric chloride formed according to the reaction: 
2Fe 3 -r6Cl= Fe 2 Cl 6 escapes the reducing influence of the iron 
on account of its volatility and collects in beautiful crystals 
in the upper part of the retort.* The process is only suc- 
cessful with complete exclusion of moisture. 

Anhydrous ferric chloride forms dark greenish, compact 
scaly masses, with a beautiful metallic gloss, dissolving 
quickly in brown drops when exposed to the air. 
Readily dissolved when vigorously warmed in water, 
alcohol and ether; with more difficulty in benzol. The 
solutions are colored brown and react acid. 



* When the chlorine current is too sluggish there may be a forma- 
tion of ferrous chloride, which then remains with the iron as 1 fused 
white mass. 



1 66 LABORATORY MANUAL OF 



FERROUS SULPHATE. 
FeS0 4 ,7H 2 0. 

Heat an excess of iron nails free from rust, or of clean 
iron wire, with dilute sulphuric acid until the evolution of 
hydrogen ceases ; filter the sufficiently concentrated solu- 
tion, add a few drops of dilute sulphuric acid to the filtrate 
and allow it to cool. Wash the crystals with water very 
slightly acidulated with sulphuric acid, dry, and keep for 
use. 

The crystals of ferrous sulphate must have a fine pale 
green color. Crystals that have been more or less oxidized 
by the action of the air and give a brownish-yellow solution 
when mixed with water, leaving undissolved ferric sulphate 
behind, may be treated as above, with sulphuric acid and 
excess of clean iron wire or nails, until the residue dissolves 
and the solution is clear pale green. Hydrogen sulphide 
must not precipitate solution of ferrous sulphate after ad- 
dition of some hydrochloric acid, nor even impart a black- 
ish tint to it. 



ANHYDROUS FERROUS BROMIDE. 
FeBr 2 . 

IOO grams of bright iron wire are vigorously heated in a 
round bottom flask on the gas stove, and ioo c. c. bromine 
distilled slowly from a water-bath into the flask. The glass 
tube conducting the bromine-vapors should reach close 
to the bottom of the flask, but the hot glass must be 
protected from fracture by the dropping bromine, 



INORGANIC PREPARATIONS. 167 

either with iron filings or a little asbestos. When the reac- 
tion begins the temperature may be somewhat moderated. 
Finally dry air or carbonic acid is passed through the 
apparatus ; upon breaking the flask the preparation is 
gathered and preserved in the same manner as described 
for ferric chloride. 



IRON AMMONIUM ALUM. 

Fe(NH 4 ) (S0 4 ) 2 -f- 12Aq. 

400 grams ferrous sulphate are dissolved in 400 c. c. water 
70 grams cone, sulphuric acid and about 120 grams of cone, 
nitric acid added to the boiling solution until a diluted 
sample mixed with ammonia shows a pure rust-colored pre- 
cipitate. Now it is evaporated until the mass is resinous 
then again diluted with water to sp. gr. 1.3 17 to 1.3 19. To 
300 grams of this ferric sulphate solution a solution of 28 
grams ammonium sulphate in 100 c. c. water is added and al- 
lowed to cool slowly and quietly. The crystals are washed 
with a little cold water and dried without warming. 

The last traces of nitric acid are removed from the fer- 
ric sulphate solution by evaporation. 

Iron alum crystals are amethyst-colored octahedra 
which must be entirely free from chlorine. Determine the 
iron value by weighing the ferric oxide which remains after 
ignition with a little ammonium nitrate. 



BERLIN BLUE. 

Hydrocyanic acid residues (page 124) are washed with 
water by decantation and rinsed in a porcelain dish with 



1 68 LABORATORY MANUAL OF 

crude hydrochloric acid. A chloride of lime emulsion 
is prepared by suspending chloride of lime in water, allow 
it to flow in, stirring well, through a funnel, the stem of 
which rests on the bottom of the dish in the hydrochloric 
acid, until the mass has turned to a nice blue color and the 
solution begins to smell of chlorine. The precipitate is 
washed with a dilute solution of common salt, as it does 
not settle in water. 

The hydrocyanic acid residues consist of the ferro-salt 
of hydrogen ferrocyanide, which is converted into ferric 
salt by the oxidizing influence of the chloride of lime. 



PURE PLATINUM. 
Pt. 

The following method of Finkener's for obtaining plati- 
num free from impurities, especially iridium, is here describ- 
ed; it depends on recrystallization of sodium platinochloride. 
Commercially purified platinum is dissolved in aqua regia, to 
the solution of the chloride, freed from oxides of nitrogen, 
the calculated amount of pure sodium chloride is added, the 
solution is concentrated to a small bulk, and allowed to cool 
whilst being continuously stirred. The crystals which sep- 
arate are freed from mother liquor by suction, washed with 
a concentrated solution of sodium chloride, and dissolved 
in a one per cent, solution of sodium carbonate. The solution 
is allowed to cool, when the salt again separates. It is 
then dried at 120 C, reduced in a current of hydrogen at a 
low temperature, and the platinum sponge thus obtained is 
washed for a long time with water, and finally dried and 
ignited. The metal thus obtained is extremely pure ; no 



INORGANIC PREPARATIONS. 1 69 

impurities could be detected in it by the methods mentioned 
above and it is calculated that it contains at least 99.99 per 
cent, of platinum.* 

It may be of interest to mention that pure platinum is 
now prepared in Germany. The method of purification is 
simpler than the English one, not involving the use of lead, 
and it yields a very pure product. In a sample of 40 grams, 
no palladium or rhodium could be detected, and only a 
trace of iridium; a trace of iron, at most 0.00 1 per cent., 
was, however, present. 



PLATINIC CHLORIDE. 

PtCU, Crystallized -f 10H 2 O. 
Heat in a clay crucible 5 parts of zinc to fusion, with 
sufficient common salt to cover the surface and prevent its 
oxidation, then introduce 1 part of platinum scraps in small 
quantities at a time into the fused metal. An alloy is 
formed from which the zinc is to be removed by digesting 
in somewhat dilute common hydrochloric acid, until all 
effervescence ceases, and subsequent boiling for a time with 
fresh hydrochloric acid. The residual platinum is com- 
pletely washed with water and boiled with nitric acid. It 
is again washed, and finally dissolved by warming with con- 
centrated hydrochloric acid and some nitric acid. Evapo- 
rate the solution on the water bath, with addition of hydro- 
chloric acid, and dissolve the semifluid residue in 10 parts 
of water for use. 



F. Myliers & Foerster, Ber. 25, 665. 



170 LABORATORY MANUAL OF 

Platinic chloride must, upon evaporation to dryness in 
the water-bath, leave a residue which dissolves completely 
in alcohol. 



PLATINIC CHLORIDE. 

From Residues. 

If the platinum residues contain alkalies and organic 
substances they are roasted in a porcelain dish on the gas 
stove, then mixed with a little diluted crude hydrochloric 
acid and reduced by zinc. The undissolved zinc is removed, 
washed and the impure metal boiled up several times with 
water and hydrochloric acid. The residue is then dissolved 
in aqua regia, evaporated to a small volume and precipita- 
ted with cone, salammoniac solution. The filtered platinum 
ammonium chloride is ignited in a porcelain crucible, the 
residue of spongy platinum boiled with HC1, dissolved in 
aqua regia, and evaporated to dryness on the water-bath in 
a weighed dish occasionally adding a few drops of HC1. 
The residue of pure platinum chloride is dissolved in 10 
parts of water. 

Ten drops of the solution with one drop of sodium chlor- 
ide solution evaporated on a watch-glass to a very small 
volume, should on cooling yield a crystalline mass, in 
which, under the microscope, only well formed, reddish-yel- 
low prisms of sodium platinum chloride are to be seen, and 
which must not be contaminated with amorphous, brown 
masses (iron; nitrogen oxide compounds of the platinum 
chloride). 



INORGANIC PREPARATIONS. 171 



PLATINOSOCHLORIDES. 

When potassium platinochloride (12 grams) is heated in 
a covered vessel, on a water-bath, with hydrogen potassium 
sulphite (9 grams) and water (160 c. c.) for 10 to 12 hours, 
the reduction is complete, and the red salt crystallizes out 
on evaporation. Similar results are obtained by heating 
the platinochloride (9 grams) with potassium hypophosphite 
(1 gram) and water (300 c. a), at 80 to 90 C, for 18 to 20 
hours. The completion of the action is shown by the pure 
ruby color of the solution, the least shade of orange indica- 
ting the presence of platinochloride. The first method is 
the safest, as the reduction cannot go beyond the platino- 
sochloride, but in the second method the red salt separates 
more easily and completely, and with care, very good re- 
sults are obtained. If, when reducing with potassium hy- 
pophosphite, the action is continued after complete 
conversion into the red salt, the solution rapidly changes to 
dark brown. Hydrochloric acid has no effect on this so- 
lution, nitric acid discolorizes it, potash causes a brown pre- 
cipitate soluble in excess of the precipitant, and ammonia a 
brown precipitate insoluble in excess.* 



SPECIALLY ACTIVE PLATINUM-BLACK. 

Very active platinum-black can be conveniently pre- 
pared as follows: — An aqueous solution (50 to 60 c. c.) of 
platinic chloride (50 grams) is mixed with 40 to 45 per 
cent, of formaldehyde solution (70 c. c), the mixture cooled 



* M. Cary Lea, Amer. Jr. Sci., 1894 [3], 48,397. 



172 LABORATORY MANUAL OF 

well, and then sodium hydroxide (50 grams) dissolved in 
water (50 grams) gradually added; after standing for 12 
hours the solution is filtered. A yellow liquid, from which 
a small quantity of platinum is deposited on boiling, first 
passes through the filter, but as scon as most of the salts 
have been washed out of the residue, !:he filtrate assumes a 
deep black color. The process is interrupted at this stage 
for several hours because the residue soon absorbs oxygen, 
the temperature rising to 36 to 40° C.,and the washings then 
pass through colorless. As soon as oxidation is complete, 
the residue is washed until completely free from sodium 
chloride, pressed, and dried over sulphuric acid. 

If the deep black filtrate referred to above is submitted 
to dialysis in absence of air, a black, transparent liquid is 
obtained which is stable in absence of air ; on exposure to 
the air, however, this liquid gradually becomes colorless, 
and a small quantity of a black powder is deposited. The 
black solution decomposes hydrogen peroxide very energet- 
ically, and when mixed with alcohol or shaken with air, the 
odor of aldehyde is immediately perceptible. These and 
other experiments seem to show that this black liquid is 
a solution of atomic platinum containing small quantities of 
organic platinum compounds.* 



PENTATHIONIC ACID. 

When 10 c. c. of decinormal sodium thiosulphate solu- 
tion are treated with a drop of a solution of potassium 
arsenite containing 1 per cent, of arsenic trioxide, and 



* A. Loew, Ber., 23, 289. 



INORGANIC PREPARATIONS. 173 

with an excess of hydrochloric acid, the solution becomes 
turbid and has a slight odor of hydrogen sulphide ; after a 
long time arsenic sulphide and a little sulphur are precipi- 
tated. When filtered, the solution gives reactions for pen- 
tathionic acid.* 



PREPARATION OF CRYSTALLIZED HYDROXY- 

LAMINE. 
A mixture of dry hydroxylamine zinc chloride (10 
grams) and anhydrous aniline (20 c. c.) is distilled under 
a pressure of 20 m.m. on a water-bath. The distillate of 
hydroxylamine, which crystallizes on cooling, is washed 
with ether, care being taken to prevent access of moist air; 
or dry ammonia gas is passed through absolute ether, hold- 
ing the zinc salt in suspension, and the decanted etherial 
solution of hydroxylamine is subsequently distilled under 
reduced pressure, when crystals are obtained. t 



HYDROXYLAMINE HYDROCHLORIDE. 

A saturated solution of sodium nitrite (1 mol.) is 
added to a solution of hydrogen sodium sulphite (2 
mols.) in a cooled vessel, and then a cold saturated solution 
of potassium chloride is added. In 24 hours hydroxyla- 
mine potassium disulphonate separates. This salt is boiled 
in water during several hours, and, on cooling, potassium 
sulphate is first deposited, and subsequently hydroxyla- 



* T. Salzer, Ber. 19, 1696. 

I L. Cris'ner, Bull. Soc. Chim. [3], 6, 793. 



174 LABORATORY MANUAL OF 

mine sulphate. A solution of this salt, treated with the 
necessary amount of barium chloride, yields the hydro- 
chloride, which can be obtained in colorless crystals, very 
hygroscopic, easily soluble in water and alcohol. It melts 
at 1 5 1 ° C, and decomposes at a higher temperature, 
yielding nitrogen, hydrogen chloride, ammonium chloride, 
and water.* 



HYDRAZINE. 

Hydrazine sulphate is best obtained when triazoacetic 
acid (250 grams in 2 litres of water) is warmed with sul- 
phuric acid (300 grams) until all effervescence ceases; the 
sulphate crystallizes out on cooling. More may be ex- 
tracted from the mother liquor by shaking with small 
quantities of benzaldehyde, thus converting the hydrazine 
into benzalazine, which separates out; after recrystalliza- 
tion this is decomposed by sulphuric acid, whereby hydra- 
zine sulphate and benzaldehyde are formed ; the latter is 
then distilled off.t 



CHYDRAZAINE OR PROTOXIDE OF 
AMMONIA. 

Chydrazai'ne is evolved when a solution of potassium 
permanganate (158 grams) and sulphuric acid (40 grams SO 3 ) 
is added to dried, crystallized ammonium oxalate (141. 2 
grams) thewhole well mixed and gently heated until it begins 

* Eichkoff, Arch. Pharm. [3], 27, 713. 

f T. Curtius and R. Jay, Jr. pr. Chem. [2], 39,27. 



INORGANIC PREPARATIONS. 175 

to boil. The gaseous product is absorbed in hydrochloric 
acid, and a neutral solution of the salt can thus be obtained. 
The hydrochloride is crystalline, and very readily soluble 
in water, but only sparingly in alcohol. The sublimed 
salt has the composition N 2 H 6 2 2HC1, but the crystals 
dried by means of the anhydrous salt contain one-fifteenth 
of their weight of water. When a solution of the hydro- 
chloride i.i mixed with platinic chloride, a platiuockloride 
is obtained, the composition of which varies with the con- 
ditions of the experiment ; with excess of the hydro- 
chloride a yellow salt is formed, the composition of which is 
approximately N 2 H 6 0,H2PtCl 6 , but if excess of platinic chlo- 
ride is added the proportion of platinum is sensibly increased. 
The sulphate is crystalline and soluble in water, but only 
sparingly so in absolute alcohol ; it forms a double-salt 
with aluminium sulphate. The nitrate is crystalline When 
a solution of the nitrate is evaporated, nitric acid, nitric 
peroxide, nitrogen, and a compound having the composi- 
tion N 2 H 2 are evolved.* 



CARBON OXYSULPHIDE 
COS. 
Is prepared by adding 50 c. c. of a concentrated aque- 
ous solution of potassium or ammonium thiocyanate to a 
cooled mixture of 290 c. c. (520 grams) of strong sul- 
phuric acid and 400 c. c. of water. The whole is heated 
at 25 ° C. in a water bath. The gas thus prepared con- 
tains only about 2.5 per cent, of carbonic anhydride and 
O.05 per cent, of carbon disulphide. The latter is absorbed 



E. J. Maumene, Bull. Soc. Chim. 49, 850. 



176 LABORATORY MANUAL OF 

by passing the gas through triethylphosphine and this in 
turn is removed by pure sulphuric acid. Carbon oxysul- 
phide is only absorbed very slowly by a 33 per cent, solu- 
tion of potash. If the gas obtained as above is passed 
slowly through about 20 c. c. of such a solution, the whole 
of the carbonic anhydride is absorbed with a loss of only 
about 7 per cent, of the oxysulphide. A 33 per cent, 
aqueous solution of potash mixed with its own volume of 
alcohol absorbs carbon oxysulphide completely and rapidly, 
and is the best reagent for use in estimating it. 

Pure carbon oxysulphide is odorless and tasteless. Its 
physiological effects are very similar to those of nitrous 
oxide. When passed through a saturated solution of 
baryta, no opalescence is produced for at least half a min- 
ute, while if any carbonic anhydride is present, the solu- 
tion becomes milky at once. With lead acetate solution, 
the precipitate is a quarter of an hour in forming.* 

NEW METHOD OF PREPARING CARBON OXYSULPHIDE. 

Carbon oxysulphide is obtained when carbonyl chloride 
is passed through concentrated sulphuric acid to dry it, 
and then through a tube 50 cm. long, filled with ignited 
asbestos well mixed with finely pulverized cadmium sul- 
phide, the tube being placed in a combustion furnace and 
heated. Even when no external heat is applied a small 
quantity of carbonyl sulphide is formed, but the most 
favorable temperature for its formation appears to be 260 to 
28o Q C. The gas thus produced is found on analysis to 
contain COS, 94.87 per cent ; CO, 3.98 per cent.; air 1.15 
per cent. A quantity of crystals, which are identified as 



* P. Klason, Jr. pr. Chem. [2], 36, 64. 



INORGANIC PREPARATIONS. IJJ 

cadmium chloride, are observed in a tube previously 
charged with a layer of cadmium sulphide and heated in a 
flame during the passage of a current of carbonyl chloride; 
the reaction, therefore, appears to be a double decompo- 
sition.* 



PURIFICATION OF CARBON DISULPHIDE. 

To one litre of carbon disulphide 0.5 c. c. bromine is 
added and allowed to remain for 3 to 4 hours. The bromine 
is then separated again by shaking the carbon disulphide 
with a slight excess of potash or by means of copper turn- 
ings. The carbon disulphide may now be opalescent, but 
this is readily removed by agitating it with a little potas- 
sium chloride, when the filtered disulphide will be obtained 
clear, colorless and of agreeable odor. It leaves no resi- 
due on evaporation^ 



* By J. Nuricsan, Ber. 24, 2967-2974. 
f A. Chenevier, L'Union pharm., 33, 204. 



1 78 LABORATORY MANUAL OF 

PREPARATION OF NORMAL SOLUTIONS OF 
ACIDS AND ALKALI. 

A normal solution contains in one litre the same num- 
ber of grams of the substance as there are units in the 
molecular weight. Example : 

Normal HC1 36.5 gms. per litre. 

HNO3 63.0 " « " 

KOH 56.1 " " " 

NaOH 40.0 " " « 

N/HC1, N/NHO g , etc., are the expressions usually used. 
These solutions are equivalent as shown by the reaction, 

HC1 + KOH = KC1 + H 2 
36.5 + 56.1 = 74.6 + 18 

The same is true of NaOH and HN0 3 ; in fact all compounds 
with single hydrogen replacing power belong to this class. 
Half Normal or N/2 solutions, as of H 2 S0 4 Na 3 C0 3 , etc., 
contain one-half of the molecular weight in the same vol- 
ume; these are equivalent to the first class, as will be seen 
by the reaction, 

H 2 S0 4 -f- 2KOH = K 2 S0 4 + H 2 
98 T122 174.2 36 

or 49 56.1 

so also with Na 2 C0 3 . 

It is impossible to weigh out any exact amount of a 
volatile liquid like HC1 or any hygroscopic solid as KOH, 
hence we must prepare these solutions indirectly. The 
following will be found to be good methods : Take pure 
dry Na 2 C0 3 , weigh off 53 grams, one-half the molecular 
weight, and dissolve in 300 to 500 c. c. of distilled water, cool 
to 15° C. and dilute to exactly one litre; now make up a 
solution of H 2 S0 4 a little more than half normal strength. 



INORGANIC PREPARATIONS. I 79 

using the hydrometer, place it in a burette, draw 10 c. c. of 
the soda solution from another burette, dilute largely with 
water, add a few drops of methyl orange (do not use 
phenolphthalein, it is acid to C0 2 ) and run in the sulphuric 
acid slowly, stirring vigorously until neutral. Example : 
10 c. c. Na 2 C0 3 require 9.8 c.c. H 2 S0 4 

Evidently if the soda solution is correct the acid is too 
strong by 0.2 c.c, therefore add 0.2 c. c. of water to every 
10 c. c. of the solution or 20 c. c. to the litre. The strength 
of the sulphuric acid may also be determined by taking any 
exact quantity, say 10 c. c, adding a drop or two of HC1 
and a slight excess of BaCl 2 , weigh the BaS0 4 and calculate 
the SO4 present ; there should be 48 grams per litre. In 
the same way make up N/HC1; the strength of this may be 
determined by AgN0 3 , either volumetric or gravimetric. In 
the first case the solution must be neutralized exactly with 
KOH or NaOH before titration; in the latter made slightly 
acid with HN0 3 . The normal hydrochloric acid has cer- 
tain advantages over sulphuric, especially in organic anal- 
ysis, as the sulphates formed during the reaction are more 
insoluble in organic liquids, alcohol, etc., than the chlor- 
ides. 

An acid solution may also be prepared by using oxalic 
acid H 2 C 2 4 , 2H 2 0, which it is possible to obtain in a state 
of great purity. In this case the water of crystallization 
must be counted in, and since the solution is N/2 or half 
normal we need 63 grams. The strength may be exactly 
determined by titration with K 2 Mn 2 8 solution, such as is 
used for iron determinations ; the solution should be warm 
and acid with sulphuric acid and the permanganate added 
until a faint pink shade is obtained 5H 2 C 2 4 +K 2 Mn 2 8 



l8o LABORATORY MANUAL OF 

+ 3H 2 S0 4 = 10CO 2 + K 2 S0 4 + 2MnS0 4 + 8H 2 0. Five 
parts of oxalic acid are equal to io parts of ferrous iron. 

The alkali solutions of KOH and NaOH are made up 
by the hydrometer stronger than necessary, cleared of 
C0 2 by the addition of a small amount of BaCl 2 and 
titrated with the standard acid (if it be H 2 S0 4 , no BaCl 2 
must be used) ; the dilution is carried out the same as 
described for H 2 S0 4 . 

In all cases the acid solutions will retain their strength 
much longer than the alkalies, they need only be protected 
from evaporation ; with the alkali the case is different. 
C0 2 , S0 2 , H 2 S, etc., are absorbed, glass is attacked, hence 
the strength should be redetermined from time to time. 

Phenolphthalein, acid colorless, alkaline pink, is the 
best indicator. It cannot be used in presence of ammo- 
nium salts and is acid to C0 2 . Methyl orange acid pink, 
alkaline yellow, is neutral to C0 2 and organic acids, and 
acts in the presence of ammonium salts. 

Table of equivalents in c. c. 

HC1 °-°365 gram. 

HN0 3 0.063 

H 2 S0 4 0.049 " 

H 2 C 2 4 , 2H 2 0.063 



H 3 PO| 


0.03266 j 


.a 


KOH 


0.0561 


a 


NaOH 


0.040 


a 


NH 4 OH 


°-°35 


a 


Na 2 CO s 


o-°53 


u 


BaOH 


0.077 


(i 



INDEX. 



Acid, Arsenic. . . 
Bismuthic 
Boracic . . . 
Dithionic. 



PAGE. 

135 

M2 

no 

99 

Hydriodic 122 

Hydrobromic 118 

Hydrochloric 15, 16 

Properties of, 16 

Hydrocyanic 124 

Hydrofluoric 125 

Hydrofluosilicic 156 

Hydrosulphuric 25 

Nitric 17 

" Properties of 19 

Perchloric 157 

Pentathionic 172 

Phosphoric 129 

Silicic, Crystalline 113 

Sulphuric 22 

" Properties of . . 24 

Alcohol, Commercial 5 

Ethyl 5 

Aluminium Chloride 114, 115 

Anhydrous, 1 17 

Hydrate n r , 

Oxide, reduction of, 116 

Alum, Iron Ammonium 167 

Ammonia 16, 30 

" Hydrate 30 

Ammonium Bicarbonate 67 

" Bromide 68 

Chloride 55 

" Properties 

of 56 

Dichromate 70 

Di Hydrogen Phos- 
phite 72 

Molybdate 54 

Nitrate 71 

Oxalate 43 

" Properties of, 44 

Persulphate 69 

Protoxide 174 

Sulphide 41 

Properties 

of 43 

Ammonio Zinc Chlorides 72 

Antimony Oxy chloride. ........ 138 

" Sulphate 143 



PAGE. 

Antimony Tritachloride 137 

Antimonious " 130 

Arsenic Pentasulphide 137 

" Trioxide 22 

Auric Chloride 83 

Auroso Auric Chloride 84 

Barium Carbonate 98 

Chloride 96 

" Dithionate 99 

" Hydroxide 35 

" Manganate 162 

" Nitrate 97 

Oxide 95 

" Perhydrate 98 

" Permanganate 162 

" Peroxide 98 

Baryta Water 35 

Berlin Blue 167 

Bismuth Hydroxide 41, 139 

" Iodide . . 140 

" Nitrate 139 

" Basic 139 

" Oxyiodide 141 

Sulphate 143 

Bismuthic Acid 142 

Borasic Acid no 

Borax, manufacture of . . .... 109 

Boron 107 

Cadmium Carbonate 94 

Caesium Compounds, Prepara- 
tion of 63 

Calcium Carbonate 89 

" Chloride 89 

" porous 87 

' ' Chromate 90 

" Hydroxide 36 

" Phosphate, crystalline. 90 

" Phosphide 131 

" Sulphide 26 

Carbon Dioxide 29 

" Disulphide 177 

" Monoxide 28 

" Oxysulphide 175 

Chlorine 10 

" Apparatus for a con- 
stant supply of ... . 12 
for Laboratory pur- 
poses 14 

" from Chloride of Lime, n 



INDEX. 



PAGE. 

Chlorine Properties of 14 

Water 10 

Chromium 149 

" Acetate . 153 

Chloride, Anhydrous, 151 

Oxide 152 

Chromyl Chloride 150 

Chydrazaine 174 

Cinnabar 104 

Cobalt Nitrate 144 

Copper Ammonium Sulphate . . 75 
Potassium " . . 75 

Cupric Sulphate 76 

Cuprous Ammonium Iodide ... 77 

Chloride 73 

" Properties of, 74 

Cyanide 74 

Oxide 76 

Phosphide 78 

Cuproammonium Tetraiodide. . 78 

Ferric Chloride 163 

Anhydrous. . . . 164 

Ferrous Bromide, Anhydrous. . 166 

" Chloride . . 164 

" Sulphate , 166 

Furnace, Roessler's 37 

Gold . 82 

" Trichloride 83 

Hydrazaine 174 

Hydrofiuosilicic Acid 156 

Hydrogen ....'. 9 

Arsenide 136 

Bromide 118 

Iodide 122 

Peroxide 145 

Phosphide 133 

Properties of 10 

Sodium Ammonium 

Phosphate . 58 
'• Sulphite ... 52 

Sulphide . 25 

" Arsenic 

fiee from . 26 
Properties 

of 27 

Hydrogen 
Arsenide, free 

from 27 

Hydroxylamine 173 



PAGE. 

Hydroxylamine Hydrochloride. 173 

Iodine Pentoxide 123 

" Trichloride 124 

Iron Ammonium Alum 167 

Lead Carbonate 39 

" Dioxide 3° 

' ' Properties of . . . 48 

' ' Tetrachloride 40 

Lime 36 

Lithium Normal Arsenate 63 

" " Phosphate ... 63 

Magnesium, Basic Carbonate . . 87 
" Carbonate, crystal- 

lized, normal. . 86 
Chloride Anhydrous, 84 

Manganese 157 

Chloride 159 

" Oxide t6o 

" Sulphate 161 

Manganous Sulphide 161 

Mercury 100 

Mercurous Bromide 107 

Mercuric Chloride. . . 103 

' ' Cyanide 104 

Mercurous Iodide 106 

Nitrate. 105 

Mercury, Purification of 102 

Mono Calcium Phosphate Crys- 
talline 90 

" Sodium Phosphite 56 

Nitrogen 10, 16 

" Properties of 10 

Tetraoxide 21 

Nitric Oxide 20 

Nitrous " 19 

Normal Solutions 17S 

Oxygen 7 

" Cubes 8 

" Properties of 8 

Phosphoric Acid 129 

Phosphorus 128 

Phosphorus Oxyfluoride 133 

Trisulphide 131 

Platinoso Chlorides 17 1 

Platinum 168 

Black 171 

" Platinic Chloride 169 

Potassa, Prepared with Baryta. 34 
Potassa, Purified with Alcohol . 33 



INDEX. 



Ill 



PAGE. 

Potassium Bisulphate 58 

Bromide 68 

Chlorate 57 

Chlorochromate 154 

Cobaltic Oxalate. . . 62 

Cyanate 60 

Cyanide 50 

Ferricyanide 59 

Hydroxide 31 

Iodide 60 

Manganate 162 

Metantimonate 62 

Nitrite 52, 53 

Properties of, 53 

Peroxide 148 

Pyroantimonate 54 

Sulphide 43 

Sulphocyanide 51 

Roessler's Furnace 37 

Rubidium Compounds, Prepar- 
ation of 63 

Salts, Preparation of, 64 

Selenium 155 

Silicon no 

" Chloride 113,114,115 

Silver 79 

' Potassium Carbonate 81 

Sodium 46 

Acetate 44 

Amalgam 9, 47 

" Ammonium Hydrogen 

Phosphate 58 

Carbonate 4S 

Free from Sul- 
phur and 
Chlorine . . 48 
Free from Sil- 
ica 48 

Properties of, 49 



PAGE. 

Sodium Chloride 45 

Dioxide 7 

Hydrogen Sulphite 52 

" Prop- 
erties of 52 

" Hydroxide 31 

Specific Grav- 
ity of Solutions of 33 

Nitrate 56 

Nitrite 53 

Peroxide 148 

" Sulphide 43 

Stannic Chloride, Anhydrous.. 127 

Stannous " 126 

" , Anhydrous . 127 

Strontium Hydroxide 92 

Salts, Preparation of, 93 

Sulphur Dichloride 148 

Dioxide 27 

" Properties of, 28 

Monochloride 148 

Titanium Trioxide 65 

Tungstates, Free from Molybde- 
num 64 

Ultramarine 117 

Vanadyl Chloride 67 

" Trichloride 66 

Volumetric Analysis 17S 

Water 1 

' ' Ammonia free 2 

Free from Organic Mat- 
ter and Ammonia. . . 2 
" Apparatus for Preparing 
free from Organic Mat- 
ter and Ammonia. ... 3, 4 

" , Chlorine 10 

Zinc free from Arsenic 91 

" Eisen 92 



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